The human fetal retinal pigment epithelium: A target tissue for thyroid hormones

Androgen Deprivation Therapy and Newly Developed Neovascular Age-Related Macular Degeneration Risk in Patients with Prostate Cancer

Background/Objectives: to evaluate the association between androgen deprivation therapy (ADT) and newly developed neovascular age-related macular degeneration (AMD) in patients with prostate cancer. Methods: We identified 228,803 men from the nationwide claims database in the Republic of Korea diagnosed with prostate cancer between 1 August 2009 and 31 December 2018 and followed until April 2021. Cases were defined as those newly diagnosed with neovascular AMD during follow-up. Cases were matched with controls based on age, index date, and follow-up duration, at a case-to-control ratio of 1:4. Adjusted odds ratios (aORs) of incident neovascular AMD associated with ADT were estimated using conditional logistic regression. Results: The main analysis included 1700 cases and 6800 controls, with a median follow-up of 3.42 years. ADT was associated with a reduced risk of incident neovascular AMD in patients with prostate cancer (aOR = 0.840; 95% confidence interval [CI], 0.743-0.951; p = 0.0058) in the multivariable analysis. A cumulative ADT duration less than 1 year was associated with a reduced risk of neovascular AMD (aOR = 0.727; 95% CI, 0.610-0.866; p = 0.0004); however, no association was observed when the duration of ADT was between 1 and 2 years (aOR = 0.862; 95% CI, 0.693-1.074; p = 0.1854) or more than 2 years (aOR = 1.009; 95% CI, 0.830-1.226; p = 0.9304). Conclusions: In patients with prostate cancer, medical castration for less than a year is associated with a reduced risk of incident neovascular AMD. These results suggest that androgens are involved in the pathogenesis of neovascular AMD.

Epidemiology of geographic atrophy and its precursor features of intermediate age-related macular degeneration

Globally age-related macular degeneration (AMD) is a leading cause of blindness with a significant impact on quality of life. Geographic atrophy (GA) is the atrophic late form of AMD and its prevalence increases markedly with age with around 1 in 5 persons aged 85 and above having GA in at least one eye. Bilateral GA leads to severe visual impairment thus posing a significant burden on patients, careers and health providers. The incidence and prevalence of GA varies across different geographic regions, with the highest rates in those of European ancestry. Although heterogeneity in definitions of GA and reporting strategy can explain some of the discrepancies, the data overall are consistent in showing a lower prevalence in other ethnicities such as those of Asian heritage. This is at present unexplained but thought to be due to the existence of protective factors such as differences in eye pigmentation, diet, environmental exposures and genetic variability. This review covers key aspects of the prevalence and incidence of the ocular precursor features of GA (large drusen, pigmentary abnormalities and reticular pseudo-drusen), the late stage of GA and factors that have been known to be associated with modifying risk including systemic, demographic, environment, genetic and ocular. Understanding the global epidemiology scenario is crucial for the prevention of and management of patients with GA.

Influence of Clinical and Genetic Factors on the Progression of Age-Related Macular Degeneration: A 3-Year Follow-Up

The aim of the present study was to analyze the relationship of age-related macular degeneration (AMD) progression with clinical characteristics, demographic, and environmental risk factors that would affect disease development. In addition, the influence of three genetic AMD polymorphisms (CFH Y402H, ARMS2 A69S, and PRPH2 c.582-67T>A) on AMD progression was investigated. In total, 94 participants with previously diagnosed early or intermediate AMD in at least one eye were recalled for an updated re-evaluation after 3 years. The initial visual outcomes, medical history, retinal imaging data, and choroidal imaging data were collected to characterize the AMD disease status. Among the AMD patients, 48 demonstrated AMD progression, and 46 showed no disease worsening at 3 years. Disease progression was significantly associated with worse initial visual acuity (OR = 6.74, 95% CI = 1.24-36.79, p = 0.03) and the presence of the wet AMD subtype in fellow eyes (OR = 3.79, 95%CI = 0.94-15.2, p = 0.05). In addition, a higher risk of AMD progression appeared in the patients with active thyroxine supplementation (OR = 4.77, CI = 1.25-18.25, p = 0.002). The CC variant of CFH Y402H was associated with AMD advancement compared to the TC+TT phenotype (OR = 2.76, 95% CI: 0.98-7.79, p = 0.05). Identifying risk factors of AMD progression may lead to earlier intervention and better outcomes, preventing the expansion of the late stage of the disease.

Biphasic expression of thyroid hormone receptor TRβ1 in mammalian retina and anterior ocular tissues

The retina is increasingly recognized as a target of thyroid hormone. We previously reported critical functions for thyroid hormone receptor TRβ2, encoded by Thrb, in cones, the photoreceptors that mediate color vision. TRβ1, another Thrb receptor isoform, is widely expressed in other tissues but little studied in the retina. Here, we investigate these N-terminal isoforms by RNA-sequencing analysis and reveal a striking biphasic profile for TRβ1 in mouse and human retina. In contrast to the early TRβ2 peak, TRβ1 peaks later during retinal maturation or later differentiation of human retinal organoids. This switch in receptor expression profiles was confirmed using lacZ reporter mice. TRβ1 localized in cones, amacrine cells and ganglion cells in contrast to the restricted expression of TRβ2 in cones. Intriguingly, TRβ1 was also detected in the retinal pigmented epithelium and in anterior structures in the ciliary margin zone, ciliary body and iris, suggesting novel functions in non-retinal eye tissues. Although TRβ1 was detected in cones, TRβ1-knockout mice displayed only minor changes in opsin photopigment expression and normal electroretinogram responses. Our results suggest that strikingly different temporal and cell-specific controls over TRβ1 and TRβ2 expression may underlie thyroid hormone actions in a range of ocular cell types. The TRβ1 expression pattern suggests novel functions in retinal and non-neural ocular tissues.

A high TSH level is associated with diabetic macular edema: a cross-sectional study of patients with type 2 diabetes mellitus

AIMS

In this study, we determined the association between thyroid-stimulating hormone (TSH) and diabetic macular edema (DME) by assessing the prevalence and risk factors for DME in type 2 diabetes mellitus (T2DM) patients with different thyroid dysfunctions.

METHODS

This was a retrospective cross-sectional study including 1003 euthyroid and 92 subclinical hypothyroidism (SCH) T2DM patients. DME status was detected by optical coherence tomography (OCT). The association between TSH and DME and the impact of TSH on DME were analyzed.

RESULTS

The DME prevalence was 28.3% in the SCH patients and 14.0% in the euthyroid population. The serum FT4 (P = 0.001) and FT3 (P < 0.001) levels were significantly higher in the non-DME group than in the DME group, and the TSH level (P < 0.001) was significantly lower. Four subgroups (G1-G4) were divided by TSH level, and the chi-square test indicated that even in the normal range, the TSH level was positively related to DME prevalence (P = 0.001). Subgroup data indicated that the association between TSH and DME detected by OCT (P = 0.001) was stronger than the correlation between TSH and diabetic retinopathy detected by digital retinal photographs (P = 0.027). The logistic regression model confirmed that elevated TSH was an independent risk factor for DME. The odds ratio was 1.53 (P = 0.02).

CONCLUSIONS

A high TSH level was an independent risk factor for DME. More attention should be given to the TSH level in T2DM patients due to its relationship with diabetic complications.

Molecular Mechanisms Underlying the Therapeutic Role of Vitamin E in Age-Related Macular Degeneration

The eye is particularly susceptible to oxidative stress and disruption of the delicate balance between oxygen-derived free radicals and antioxidants leading to many degenerative diseases. Attention has been called to all isoforms of vitamin E, with α-tocopherol being the most common form. Though similar in structure, each is diverse in antioxidant activity. Preclinical reports highlight vitamin E’s influence on cell physiology and survival through several signaling pathways by activating kinases and transcription factors relevant for uptake, transport, metabolism, and cellular action to promote neuroprotective effects. In the clinical setting, population-based studies on vitamin E supplementation have been inconsistent at times and follow-up studies are needed. Nonetheless, vitamin E’s health benefits outweigh the controversies. The goal of this review is to recognize the importance of vitamin E’s role in guarding against gradual central vision loss observed in age-related macular degeneration (AMD). The therapeutic role and molecular mechanisms of vitamin E’s function in the retina, clinical implications, and possible toxicity are collectively described in the present review.

Deficiency of thyroid hormone receptor protects retinal pigment epithelium and photoreceptors from cell death in a mouse model of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly. Progressive dystrophy of the retinal pigment epithelium (RPE) and photoreceptors is the characteristic of dry AMD, and oxidative stress/damage plays a central role in the pathogenic lesion of the disease. Thyroid hormone (TH) regulates cell growth, differentiation, and metabolism, and regulates development/function of photoreceptors and RPE in the retina. Population-/patient-based studies suggest an association of high free-serum TH levels with increased risk of AMD. We recently showed that suppressing TH signaling by antithyroid treatment reduces cell damage/death of the RPE and photoreceptors in an oxidative-stress/sodium iodate (NaIO₃)-induced mouse model of AMD. This work investigated the effects of TH receptor (THR) deficiency on cell damage/death of the RPE and photoreceptors and the contribution of the receptor subtypes. Treatment with NaIO₃ induced RPE and photoreceptor cell death/necroptosis, destruction, and oxidative damage. The phenotypes were significantly diminished in Thrα1^−/−, Thrb^−/−, and Thrb2^−/− mice, compared with that in the wild-type (C57BL/6 J) mice. The involvement of the receptor subtypes varies in the RPE and retina. Deletion of Thrα1 or Thrb protected RPE, rods, and cones, whereas deletion of Thrb2 protected RPE and cones but not rods. Gene-expression analysis showed that deletion of Thrα1 or Thrb abolished/suppressed the NaIO₃-induced upregulation of the genes involved in cellular oxidative-stress responses, necroptosis/apoptosis signaling, and inflammatory responses. In addition, THR antagonist effectively protected ARPE-19 cells and hRPE cells from NaIO₃-induced cell death. This work demonstrates the involvement of THR signaling in cell damage/death of the RPE and photoreceptors after oxidative-stress challenge and the receptor-subtype contribution. Findings from this work support a role of THR signaling in the pathogenesis of AMD and the strategy of suppressing THR signaling locally in the retina for protection of the RPE/retina in dry AMD.

Thyroid disease is associated with higher age-related macular degeneration risk: results from a meta-analysis of epidemiologic studies

BACKGROUND

Although epidemiologic studies have suggested that thyroid disease may be a risk factor for age-related macular degeneration (AMD), this finding is still controversial.

OBJECTIVES

The aim of this meta-analysis was to investigate whether an association exists between thyroid disease and medication and AMD in epidemiologic studies.

METHODS

We searched PubMed, EMBASE, and Google Scholar from their inception to March 2020 for cross-sectional, case-control and cohort studies that assessed thyroid function and AMD risk. Data from selected studies were extracted, and a meta-analysis was performed using fixed-effect or random-effect models. The statistical heterogeneity (I2) among studies and the possibility of publication bias were evaluated. If I2 > 50%, a significant heterogeneity existed among studies and a random effects model was used to calculate the pooled RR. Otherwise, a fixed-effects model was performed.

RESULTS

A total of 13 epidemiologic studies that consisted of 7 thyroid disease and 7 thyroid medication studies were included. Statistically significant heterogeneity was observed in the study results (I2 thyroid disease = 80.1%, I2 thyroid medication = 69.0%). A significant positive association was found between thyroid disease and AMD, with an overall relative risk (RR) of 1.25 (95% CI: 1.02, 1.54). However, there was no statistical association between thyroid medication and AMD risk (pooled RR 1.26 [95% CI 0.92-1.72]). Egger's test indicated that there was no significant publication bias for thyroid disease (P=0.889) or thyroid medication (P = 0.226).

CONCLUSIONS

Our findings indicate that thyroid disease is associated with higher AMD risk. Thyroid disease prevention strategies may have a significant effect on the prevention of AMD and warrant further evaluation.

Thyroid and Eye: Where They Meet in Clinical Practice

OBJECTIVE

Thyroid Hormones (TH) are essential for normal growth, development and continued optimal function of most of the body organs including the eye. TH signaling plays a central role in the regulation of retinal development and maturation. Deficiency in TH during fetal and early postnatal development impairs growth of the eye and proliferation of all retinal cell types. The present article reviews the most important topics of the different derangements in thyroid function and structure and its relation with eye diseases.

METHODS

A literature search strategy was conducted for all English-language literature.

RESULTS

From a clinical practice viewpoint, it should be mentioned that both hypothyroidism and hyperthyroidism are accompanied by ocular diseases i.e. thyroid-associated ophthalmopathy, diabetic retinopathy and age-related macular degeneration. Although the orbit and globe are not common sites for metastatic thyroid cancers, orbital metastasis may be the primary clinical manifestation of thyroid carcinoma. Finally, some medications as amiodarone may be accompanied by both thyroid dysfunction and adverse ocular events.

CONCLUSION

Thyroid disorders and eye diseases are interrelated through several mechanisms thus, awareness of this relation has a great impact on early diagnosis and treatment.

Risk factors for progression of age-related macular degeneration

Purpose

Age‐related macular degeneration (AMD) is a degenerative disease of the macula, often leading to progressive vision loss. The rate of disease progression can vary among individuals and has been associated with multiple risk factors. In this review, we provide an overview of the current literature investigating phenotypic, demographic, environmental, genetic, and molecular risk factors, and propose the most consistently identified risk factors for disease progression in AMD based on these studies. Finally, we describe the potential use of these risk factors for personalised healthcare.

Recent findings

While phenotypic risk factors such as drusen and pigment abnormalities become more important to predict disease progression during the course of the disease, demographic, environmental, genetic and molecular risk factors are more valuable at earlier disease stages. Demographic and environmental risk factors such as age and smoking are consistently reported to be related to disease progression, while other factors such as sex, body mass index (BMI) and education are less often associated. Of all known AMD variants, variants that are most consistently reported with disease progression are rs10922109 and rs570618 in CFH, rs116503776 in C2/CFB/SKIV2L, rs3750846 in ARMS2/HTRA1 and rs2230199 in C3. However, it seems likely that other AMD variants also contribute to disease progression but to a lesser extent. Rare variants have probably a large effect on disease progression in highly affected families. Furthermore, current prediction models do not include molecular risk factors, while these factors can be measured accurately in the blood. Possible promising molecular risk factors are High‐Density Lipoprotein Cholesterol (HDL‐C), Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), zeaxanthin and lutein.

Summary

Phenotypic, demographic, environmental, genetic and molecular risk factors can be combined in prediction models to predict disease progression, but the selection of the proper risk factors for personalised risk prediction will differ among individuals and is dependent on their current disease stage. Future prediction models should include a wider set of genetic variants to determine the genetic risk more accurately, and rare variants should be taken into account in highly affected families. In addition, adding molecular factors in prediction models may lead to preventive strategies and personalised advice.

Thyroid function and age-related macular degeneration: a prospective population-based cohort study--the Rotterdam Study

BACKGROUND

In animal models, lack of thyroid hormone is associated with cone photoreceptor preservation, while administration of high doses of active thyroid hormone leads to deterioration. The association between thyroid function and age-related macular degeneration (AMD) has not been investigated in the general population.

METHODS

Participants of age ≥ 55 years from the Rotterdam Study with thyroid-stimulating hormone (TSH) and/or free thyroxine (FT4) measurements and AMD assessment were included. We conducted age- and sex-adjusted Cox proportional hazards models to explore the association of TSH or FT4 with AMD, in the full range and in those with TSH (0.4-4.0 mIU/L) and/or FT4 in normal range (11-25 pmol/L). Cox proportional hazards models were performed for the association of TSH or FT4 with retinal pigment alterations (RPA), as an early marker of retinal changes. Multivariable models additionally included cardiovascular risk factors and thyroid peroxidase antibodies positivity. We also performed stratification by age and sex. A bidirectional look-up in genome-wide association study (GWAS) data for thyroid parameters and AMD was performed. Single nucleotide polymorphisms (SNPs) that are significantly associated with both phenotypes were identified.

RESULTS

We included 5,573 participants with a median follow-up of 6.9 years (interquartile range 4.4-10.8 years). During follow-up 805 people developed AMD. TSH levels were not associated with increased risk of AMD. Within normal range of FT4, participants in the highest FT4 quintile had a 1.34-fold increased risk of developing AMD, compared to individuals in the middle group (95% confidence interval [CI] 1.07-1.66). Higher FT4 values in the full range were associated with a higher risk of AMD (hazard ratio 1.04, CI, 1.01-1.06 per 1 pmol/L increase). Higher FT4 levels were similarly associated with a higher risk of RPA. Restricting analyses to euthyroid individuals, additional multivariable models, and stratification did not change estimates. We found a SNP (rs943080) in the VEGF-A gene, associated with AMD, to be significant in the TSH GWAS (P = 1.2 x 10(-4)). Adding this SNP to multivariable models did not change estimates.

CONCLUSIONS

Higher FT4 values are associated with increased risk of AMD - even in euthyroid individuals - and increased risk of RPA. Our data suggest an important role of thyroid hormone in pathways leading to AMD.

Regulated expression of apolipoprotein E by human retinal pigment epithelial cells

In early age-related macular degeneration (AMD), lipid-containing deposits (drusen) accumulate in Bruch's membrane underlying the retinal pigment epithelium (RPE). Recent studies indicate that apolipoprotein E (apoE) may play a role in lipid trafficking in AMD. Compared with the apoE3 allele, the apoE4 and apoE2 alleles are associated with decreased and increased risk for AMD, respectively; drusen contain high levels of apoE, and apoE null mice develop lipid deposits in Bruch's membrane similar to those observed in AMD. Primary cultures of human RPE cells expressing the apoE3 allele were grown on Transwell culture plates. Western blotting, ELISA assay, and mass spectrometry confirmed that apoE3 was secreted into the apical and basal chambers and that secretion was upregulated by thyroid hormone, 9-cis-retinoic acid, and 22(R)-hydroxycholesterol. In addition, basally secreted apoE associated with exogenously added HDL. These results indicate that apoE secretion can be regulated by specific hormones and that apoE associates with HDL. The findings are consistent with a role for apoE in lipid trafficking through Bruch's membrane and may be relevant to AMD.

Human retinal pigment epithelial cells express scavenger receptors BI and BII

The retinal pigment epithelial (RPE) cells that underlie the retina ingest and metabolize thousands of lipid-rich photoreceptor outer segments (POS) every day. The scavenger receptor (SR) CD36 and integrin alphavbeta5 have been shown to participate in POS binding and internalization by RPE cells. The objective of the current study was to determine whether RPE cells express SRs other than CD36. Primary cultures of human RPE cells express both mRNA and protein for SR-BI and SR- BII. SR-BI and SR-BII mRNAs were detected by reverse transcription-polymerase chain reaction. SR-BI protein was detected by immune precipitation of [(35)S]methionine-labeled crude cellular extracts. SR-BII was detected by Western blotting of immune precipitated crude cellular extracts. SR-BI and SR-BII proteins were also detected by immunofluorescence staining of RPE cells in culture. The results suggest that these SRs may play a role in POS lipid binding and uptake by RPE cells in the eye.