Clinical course and visual outcome in patients with diabetes mellitus and uveitis

Clinical Profile and Ocular Morbidities in Patients with Both Diabetic Retinopathy and Uveitis

Purpose

To describe the clinical profile and complications of diabetic retinopathy (DR) and uveitis in patients with coexisting conditions and to derive associations based on site of primary inflammation, stage of DR, and complications of each.

Design

Single-center, cross-sectional observational study.

Participants

Sixty-six patients with coexisting DR and uveitis.

Methods

Electronic medical records of 66 such cases were evaluated. The demographic data, diabetic status, clinical characteristics, and complications of DR and uveitis on the final follow-up were recorded.

Main Outcome Measures

Associations between best corrected visual acuity (BCVA), prevalence of various stages, and complications of DR among eyes with and without uveitis, and correlation between the intensity and primary sites of inflammation among eyes with proliferative and nonproliferative changes.

Results

Of the 132 eyes, all had DR and 97 eyes had uveitis (35 unilateral and 31 bilateral cases). Mean age of patients was 53.4 ± 8.7 years, duration of diabetes was 10.5 ± 6.9 years, and duration of uveitis was 61.3 ± 68.8 months. Of uveitis patients, 54.6% had anterior uveitis (AU), 20.6% had intermediate, 10.3% posterior, and 14.4% panuveitis. Forty-nine point five percent of eyes had proliferative DR (PDR) changes. There was a higher proportion PDR cases among anterior (56.6%), posterior (70%), and panuveitis (64.3%), with difference in AU cases approaching statistical significance (P = 0.067). Conversely, significant (P < 0.001) intermediate uveitis cases had nonproliferative changes (80%). Final BCVA was significantly poorer in the group with uveitis (P = 0.045). The proportion of fibrovascular proliferations, tractional detachments. and iris neovascularization among proliferative retinopathy eyes with uveitis (14.6%, 18.8%, and 12.5% respectively) was higher than those without uveitis (5.3%, 10.5%, and 5.3%). Among uveitis cases, 58.5% eyes developed cataracts, 44.3% had posterior synechiae, 12.3% developed secondary glaucoma, 4.1% had epiretinal membrane, 4.1% had band-shaped keratopathy, and 1.0% developed macular neovascularization.

Conclusions

Eyes with coexisting DR and uveitis have a higher prevalence of neovascular and uveitis complications along with a risk of poorer visual outcomes. Treatment should aim at limiting the duration and intensity of inflammation. Strict glycemic control is essential for inflammation control and preventing the progression of DR to more advanced stages.

Financial Disclosures

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

Diabetes, Diabetic Retinopathy, and Inflammatory Disorders

This review summarizes the impact of systemic and ocular inflammatory disorders on diabetes mellitus (DM) and diabetic retinopathy (DR). Local inflammation is a key pathology in diabetic retinopathy (DR) and is also an evolving target for clinical therapy. The legacy effects of local inflammation at the intracellular level make DR a persistent self-driven vicious process. Ocular inflammation is accompanied as well as incited by systemic inflammation due to diabetes mellitus (DM) itself. Over the years, a multitude of studies have evaluated the impact of systemic inflammatory disorders (SIDs, like rheumatoid arthritis, lupus, psoriasis, etc.) and anti-inflammatory drugs prescribed for managing them on manifestations of DM. Recent studies have indicated increased insulin resistance to be a result of chronic inflammation, and the anti-inflammatory drugs to have a protective effect towards DM. Very few studies have evaluated the impact of SIDs on DR. Furthermore, the evidence from these studies is conflicting, and while local anti-inflammatory therapy has shown a lot of clinical potential for use in DR, the results of systemic anti-inflammatory therapies have been inconsistent. The impact of local ocular inflammation due to uveitis on DR is a crucial aspect that has not been evaluated well at present. Initial pre-clinical studies and small-sized clinical reports have shown a strong and positive relationship between the presence of uveitis and the severity of DR as well as its progression, while larger cross-sectional patient surveys have refuted the same. The long term impact of ocular inflammation due to uveitis on DR needs to be studied while adjusting for confounders.

Diabetes Mellitus Related Anterior Uveitis - An Overlooked Clinical Entity

BACKGROUND

This study aimed to evaluate the characteristics of anterior uveitis in patients presenting with poorly controlled diabetes mellitus and with no other identifiable cause for their uveitis.

METHODS

A retrospective study of 121 eyes in 89 patients who presented at Auckland District Health Board with idiopathic acute anterior uveitis and uncontrolled diabetes between September 2009 and January 2022.

RESULTS

The diagnosis of diabetes mellitus was known prior to presentation in 80 subjects (89.9%) and was discovered as a result of screening tests in the remainder. Mean HbA1c at presentation was 117.3 mmol/mol. Most uveitis was severe with 3+ (30 eyes, 25.4%) or 4+ cells (30 eyes, 25.4%) in the anterior chamber. Recurrence occurred in 22 eyes (18.2%) and was associated with elevated HbA1c. The visual prognosis was good with median visual acuity at 12 months of 6/7.5.

CONCLUSION

Poorly controlled diabetes can be associated with acute anterior uveitis.

Analyzing the demographics of patients with uveitis in an indigent, urban population

PURPOSE

To study the types of uveitis examined in a hospital serving indigent populations in need of low-cost care.

METHODS

A retrospective chart review examined the electronic medical records of all patients with uveitis-related at Drexel Eye Physicians. Data collected included demographics, anatomic location of the uveitis, systemic disease associations, treatment modalities and insurance. Statistical analysis was performed using χ² or Fischer exact tests.

RESULTS

270 patients (366 eyes) were included for analysis, 67% of patients identified as African American. Most eyes (95.3%, N = 349) were treated with topical corticosteroid drops, and only 6 (1.6%) received an intravitreal implant. Immunosuppressive medications were started in 24 patients (8.9%). Nearly 80% depended to some extent on Medicare or Medicaid Assistance for treatment coverage. There was no association between insurance type and use of biologics or difluprednate.

CONCLUSION

We found no association between insurance type and the prescription of medications for uveitis that should be used at home. There was a minimal number of patients prescribed medications for implantation in the office. The adherence of use of medications at home should be investigated.

Treatment approaches to postoperative fibrinoid syndrome after phacoemulsification

BACKGROUND: Postoperative fibrinoid syndrome (PFS) is an early complication of phacoemulsification, manifested by fibrin deposition on the iris and the intraocular lens surface, which leads to visual acuity decrease. AIM: To assess the rate and the treatment efficacy (by YAG laser, enzymatic, medicalmentous) in PFS after phacoemulsification. MATERIALS AND METHODS: Retrospective analysis of 56,019 cataract surgery cases of 20172021. There were 49 patients with PFS divided into 3 groups according to treatment approaches: 1st group medicamentous treatment (MT) + YAG laser destruction of the fibrin film (n = 6); 2nd MT + prourokinase injection into the anterior chamber (n = 6); 3rd MT only (n = 37). RESULTS: There was no difference between groups in best-corrected visual acuity (BCVA) before the PFS development. There was a more rapid increase in BCVA in the 1st and the 2nd groups compared with the 3rd one on the third day (0.20 0.09 and 0.21 0.08 versus 0.09 0.08 for groups respectively, p = 0.001) and on the fifth day of treatment (0.25 0.10 and 0.27 0.13 versus 0.16 0.14, p = 0.029). Nevertheless, in one week, there was no difference in BCVA between groups. Unfortunately, BCVA did not return to baseline in any group. CONCLUSION: The incidence of PFS after phacoemulsification is relatively low and amounts to 0.093%. The most rapid BCVA recovery was observed in the 1st and the 2nd groups.

Chronic Kidney Disease as A Potential Risk Factor for Uveitis: A 13-Year Nationwide Population-Based Cohort Study in Taiwan

PURPOSE

To investigate whether patients with chronic kidney disease (CKD) are at increased risk of uveitis.

METHODS

Data was collected from the Taiwan National Health Insurance system and included patients newly diagnosed with CKD between 2000 and 2012. The endpoint of interest was a diagnosis of uveitis.

RESULTS

30,256 CKD patients and 121,024 matched comparisons were analyzed. CKD patients were found to have a significantly higher cumulative uveitis incidence. Through multivariate Cox regression analysis, the CKD group was found to have higher risk of developing uveitis (adjusted hazard ratio 1.51). After stratified by gender, age, and comorbidities (hypertension, diabetes, and hyperlipidemia), the increased risk of uveitis in CKD patients remained significant.

CONCLUSIONS

Patients with CKD were found to have higher risk of developing uveitis. For patients over 18 years old and with hypertension, diabetes, or hyperlipidemia, the presence of CKD was demonstrated as an additional crucial factor for uveitis development.

Asymmetric diabetic retinopathy

Increasing prevalence of diabetes mellitus warrants recognition of factors related to asymmetric diabetic retinopathy (DR). This thematic synthesis based on an iterative literature review conducted in Medline and Google Scholar pertaining to diabetes with coexistent asymmetry of retinopathy included 45 original articles, 21 case reports and series, and 18 review articles from 1965 to 2020. Asymmetric DR is defined as proliferative DR (PDR) in one eye and nonproliferative, preproliferative, background, or no DR in the other eye lasting for at least 2 years. It is observed in 5%–10% of patients with PDR. Associated factors can be divided into (i) vascular: carotid obstructive disease, ocular ischemic syndrome, and retinal vascular diseases; (ii) Inflammatory: uveitis, endophthalmitis, and Fuchs’ heterochromic cyclitis; (iii) degenerative: posterior vitreous detachment, high myopia and anisometropia, uveal coloboma, retinal detachment, retinitis pigmentosa, and chorioretinal atrophy and scarring; (iv) cataract surgery and vitrectomy; and (v) miscellaneous: elevated intraocular pressure, glaucoma, amblyopia, retinal detachment, and optic atrophy. The gamut of diagnostic modalities for asymmetric DR includes thorough ocular examination, slit-lamp biomicroscopy, fundus photography, fundus fluorescein angiography, optical coherence tomography, and newer modalities such as ultra-widefield fluorescein angiography and optical coherence tomography angiography, along with a complete systemic evaluation and carotid Doppler studies. The differential diagnosis includes other causes of retinal neovascularization that may present in an asymmetric manner, such as sickle cell retinopathy, retinal vein occlusions, and featureless retina. This review discusses in detail the aforementioned considerations and draws a comprehensive picture of asymmetric DR in order to sensitize ophthalmologists to this important condition.

Incidence and changing patterns of uveitis in Central Tokyo

PURPOSE

The patterns of uveitis in Tokyo have recently changed due to advances in examination tools. We aimed to investigate the changes in the patterns of uveitis between 2004-2015 and 2016-2018.

METHODS

We retrospectively reviewed the data of 732 patients who visited the Uveitis Clinic at the University of Tokyo Hospital between January 2016 and December 2018. Background characteristics, laboratory results, and imaging findings were analysed. We compared the incidences of uveitis in 2016-2018 and 2004-2015 to identify changes in the patterns.

RESULTS

The most frequent diagnoses were sarcoidosis (8.9%), herpetic iridocyclitis (6.7%), intraocular lymphoma (5.5%), Vogt-Koyanagi-Harada disease (4.8%), unclassified acute anterior uveitis (4.6%), Behçet's disease (4.5%), bacterial endophthalmitis (2.9%), and Posner-Schlossman syndrome (2.6%). Suspected sarcoidosis (20.9%) was the most common cause of unclassified uveitis. The incidence of intraocular lymphoma was significantly higher in 2016-2018 than in 2004-2015. Between 2004 and 2018, herpetic iridocyclitis, bacterial endophthalmitis, and juvenile chronic iridocyclitis exhibited an increasing trend, and the incidences of Posner-Schlossman syndrome, unclassified acute anterior uveitis, Behçet's disease, and Vogt-Koyanagi-Harada disease exhibited a decreasing trend.

CONCLUSION

The changing patterns of uveitis were characterised by increases in the incidence of intraocular lymphoma. This may be attributed to recent advances in examination tools, the changes in the referred patient population, and the aging Japanese population.

Association between islet autoantibodies and the prevalence of autoimmune uveitis

AIM

To evaluate the predictive value of islet autoantibodies for the diagnosis of autoimmune uveitis (AU), as well as to characterize the association bet ween islet autoantibodies and AU.

METHODS

Totally 97 patients with AU and 100 healthy persons without any autoimmune diseases as the control group were recruited. Multiple serum islet autoantibodies were measured using commercial enzyme-linked immunosorbent assay kits (ELISA). A supplementary questionnaire was used to complement the subject's demographics and clinical features. The level of glucose concentrations and white blood cells were measured. Conditional logistic regression was performed to estimate odds ratios (ORs), and 95% confidence intervals (CIs) of AU according to islet autoantibodies and to evaluate the predictive value of islet autoantibodies for AU diagnosis. Autoantibodies subgroups and other variables were included into analysis.

RESULTS

In AU patients, the prevalence of detecting at least one of the autoantibodies was 31.9% (31/97). The most frequent autoantibody was ZnT8A (30.9%), followed by GADA (11.3%), IA-2A (4.1%), ICA (2.1%) and IAA (2.1%). Islet autoantibodies were found to be correlated positively with AU diagnosis [OR (95%CI): 13.86 (3.28, 58.50), P<0.001]. Moreover, Zn-T8A was remarkably correlated with AU diagnosis [OR (95%CI): 6.13 (1.96, 19.17), P<0.001], In contrast, neither GADA nor other islet antibodies (IA-2A, ICA and IAA) showed any association with AU risk under an additive model.

CONCLUSION

The prevalence of islet antibodies, especially ZnT8A, in patients with AU is higher. Islet antibodies as well as novel biomarkers should be included in routine evaluation at AU and is a valuable biological marker to classify newly-diagnosed uveitis.

Relationship between Uveitis and Thyroid Disease: A 13-Year Nationwide Population-based Cohort Study in Taiwan

PURPOSE

To investigate whether patients with thyroid disease are at increased risk of uveitis.

METHODS

Data was collected from the Taiwan National Health Insurance system and included patients newly diagnosed with thyroid disease from 2000 to 2012. The endpoint of interest was a diagnosis of uveitis.

RESULTS

In analyzing 21,396 patients with thyroid disease, yielding 85,584 matched comparisons, patients with thyroid disease to have a significantly higher cumulative incidence of uveitis when compared to the control cohort with the Kaplan-Meier analysis. This result was further confirmed by Cox regression analysis. The increased risk was persistent in both genders. The association between thyroid disease and uveitis was stronger in patients without diabetes or hypertension.

CONCLUSION

Patients with thyroid disease were found to have a higher risk for uveitis. For certain age groups or patients without diabetes or hypertension, the role of thyroid disease might be more crucial for uveitis development.

Kallistatin Attenuates Experimental Autoimmune Uveitis by Inhibiting Activation of T Cells

Experimental autoimmune uveoretinitis (EAU) is a mouse model of human autoimmune uveitis. EAU spontaneously resolves and is marked by ocular autoantigen-specific regulatory immunity in the spleen. Kallikrein binding protein (KBP) or kallistatin is a serine proteinase inhibitor that inhibits angiogenesis and inflammation, but its role in autoimmune uveitis has not been explored. We report that T cells activation is inhibited and EAU is attenuated in human KBP (HKBP) mice with no significant difference in the Treg population that we previously identified both before and after recovery from EAU. Moreover, following EAU immunization HKBP mice have potent ocular autoantigen specific regulatory immunity that is functionally suppressive.

Exacerbation of autoimmune uveitis by obesity occurs through the melanocortin 5 receptor

Autoimmune uveitis is a leading cause of blindness with a complex etiology. Obesity is considered a chronic disease with a connection with autoimmune diseases through systemic inflammation. However, an obesity and autoimmune disease connection is not consistently true in rodent models of autoimmune disease. A mouse model of human autoimmune uveitis, experimental autoimmune uveitis (EAU) has been used to better understand the immunobiology of uveitis. In this study, we assessed EAU in a high-fat diet (HFD) obesity model and found that the EAU severity is significantly higher in wild-type mice, but not in HFD melanocortin 5 receptor deficient mice. We find a decrease in CD11b⁺ F4/80⁺ Ly-6C^lo Ly-6G⁺ Mϕs, previously shown to be suppressive, and an enhancement of a Th1 response at the onset of EAU in obese mice. We further demonstrate that at recovery of EAU, obese mice lack regulatory immunity that provides protection from EAU. This report demonstrates that obesity exacerbates autoimmune uveitis and inhibits the promotion of post-EAU regulatory immunity through the melanocortin 5 receptor. The implication of this work is that obesity may contribute to the prevalence of autoimmune uveitis.

Intravitreal pro-inflammatory cytokines in non-obese diabetic mice: Modelling signs of diabetic retinopathy

Diabetic retinopathy is a vascular disease of the retina characterised by hyperglycaemic and inflammatory processes. Most animal models of diabetic retinopathy are hyperglycaemia-only models that do not account for the significant role that inflammation plays in the development of the disease. In the present study, we present data on the establishment of a new animal model of diabetic retinopathy that incorporates both hyperglycaemia and inflammation. We hypothesized that inflammation may trigger and worsen the development of diabetic retinopathy in a hyperglycaemic environment. Pro-inflammatory cytokines, IL-1β and TNF-α, were therefore injected into the vitreous of non-obese diabetic (NOD) mice. CD1 mice were used as same genetic background controls. Fundus and optical coherence tomography images were obtained before (day 0) as well as on days 2 and 7 after intravitreal cytokine injection to assess vessel dilation and beading, retinal and vitreous hyper-reflective foci and retinal thickness. Astrogliosis and microgliosis were assessed using immunohistochemistry. Results showed that intravitreal cytokines induced vessel dilation, beading, severe vitreous hyper-reflective foci, retinal oedema, increased astrogliosis and microglia upregulation in diabetic NOD mice. Intravitreal injection of inflammatory cytokines into the eyes of diabetic mice therefore appears to provide a new model of diabetic retinopathy that could be used for the study of disease progression and treatment strategies.

Epidemiology of uveitis (2013-2015) and changes in the patterns of uveitis (2004-2015) in the central Tokyo area: a retrospective study

Background

The distribution of uveitis varies with genetic, ethnic, geographic, environmental, and lifestyle factors. Epidemiological information about the patterns of uveitis is useful when an ophthalmologist considers the diagnosis of uveitis. Therefore, it is important to identify the causes of uveitis over the years in different regions. The purposes of this study were to characterize the uveitis patients who first arrived at the University of Tokyo Hospital in 2013–2015, and to analyze the changes in the patterns of uveitis from 2004 to 2012 to 2013–2015.

Methods

We retrospectively identified 750 newly arrived patients with uveitis who visited the Uveitis Clinic in the University of Tokyo Hospital between January 2013 and December 2015, using clinical records. We extracted data on patient age, sex, diagnosis, anatomic location of inflammation, laboratory test results of blood and urine, and chest X-ray and fluorescein fundus angiography findings for each patient. In addition, we compared these data with those from 2004 to 2012 to analyze the changes in the patterns of uveitis.

Results

A definite diagnosis was established in 445 patients (59.3%). The most common diagnoses were herpetic iridocyclitis (7.5%), sarcoidosis (6.1%), Behçet’s disease (4.4%), Vogt–Koyanagi–Harada disease (4.1%), and intraocular lymphoma (4.1%). The most frequent unclassified type of uveitis was suspected sarcoidosis (22.3%). Analysis of the changes in the patterns of uveitis in the central Tokyo area from 2004 to 2012 to 2013–2015 revealed notable increasing trends of herpetic iridocyclitis and intraocular lymphoma, and increasing trends of bacterial endophthalmitis, fungal endophthalmitis, and juvenile chronic iridocyclitis. In contrast, the frequency of sarcoidosis, Behçet’s disease, and Vogt–Koyanagi–Harada disease decreased.

Conclusions

The patterns of uveitis changed considerably from 2004 to 2012 to 2013–2015. Continuous investigations about the epidemiology of uveitis are needed to diagnose uveitis more accurately.

Glycemic control is an important modifiable risk factor for uveitis in patients with diabetes: A retrospective cohort study establishing clinical risk and ophthalmic disease burden

AIM

To characterize the risk uveitis, scleritis or episcleritis in relation to diabetes, glycaemic control, and co-existence of retinopathy.

METHODS

Using the Royal College of General Practitioners Research and Surveillance Centre database, we established the prevalence of acute uveitis and scleritis or episcleritis over a six-year period among populations without(n = 889,856) and with diabetes(n = 48,584). We evaluated the impact of glycaemic control on disease risk. Regression modeling was used to identify associations, adjusting for clinical and demographic confounders.

RESULTS

Incidence of acute uveitis was higher among patients with diabetes; Type 1 OR:2.01 (95% CI 1.18-3.41; p = 0.009), and Type 2 OR:1.23 (1.05-1.44; p = 0.01). Glycaemic control was established as an important effect modifier for uveitis risk, whereby those with poorer control suffered higher disease burden. Results confirmed a dose-response relationship such that very poor glycaemic control OR:4.72 (2.58-8.65; p < 0.001), poor control OR:1.57 (1.05-2.33; p = 0.03) and moderate control OR:1.20 (0.86-1.68; p = 0.29) were predictive of uveitis. Similar results were observed when evaluating retinopathy staging: proliferative retinopathy OR:2.42 (1.25-4.69; p = 0.01). These results were not maintained for scleritis or episcleritis.

CONCLUSION

Acute uveitis is more common in patients with diabetes; at highest risk are those with type 1 disease with poor glycaemic control. Glycaemic improvements may prevent recurrence.

Clinical features of patients with diabetic anterior uveitis

AIM

To describe clinical features and outcomes of new-onset anterior uveitis associated with poorly controlled or undiagnosed diabetes mellitus.

METHODS

Retrospective analysis of 25 eyes of 18 patients (14 men, 4 women; mean age 44 years) who presented between December 2001 and October 2016 to the Kyorin Eye Center.

RESULTS

Ocular findings at presentation included posterior synechiae (15 eyes, 60%), anterior chamber fibrin (13 eyes, 52%), keratic precipitates (10 eyes, 40%), Descemet membrane folds (7 eyes, 28%) and hypopyon (3 eyes, 12%). Seven cases were bilateral. Intraocular pressure >21 mm Hg (7 eyes, 28%) and diabetic retinopathy (7 eyes, 28%, all non-proliferative) were also noted. The mean random blood glucose was 332 mg/dL (range 135-604 mg/dL) and the mean haemoglobin A1c was 12.6% (range 9.7%-16.7%). Seven patients (39%) were unaware of their hyperglycaemic state, and the remainder had either poor glucose control or had discontinued their diabetes treatment. Systemic examination and ancillary testing ruled out other possible causes of the uveitis. The ocular inflammation was managed in all cases using local corticosteroid therapy (drops and subconjunctival injections) in addition to internal medicine intervention for the diabetes. The best-corrected visual acuity (BCVA) was improved or maintained in all eyes at 3 months. The BCVA was ≤0.5 in two eyes due to both cataract and diabetic macular oedema.

CONCLUSIONS

We characterised new-onset anterior uveitis in 18 patients in association with poorly controlled or undiagnosed diabetes mellitus. The uveitis was managed in all cases with local corticosteroid therapy in addition to proper diabetes systemic treatment.

Intraocular Inflammation in Diabetic Populations

PURPOSE OF REVIEW

The purpose of this review is to determine the prevalence of uveitis in the diabetic population, the clinical features of the uveitis and diabetes when coexisting and pathophysiology of a possible correlation. We also aim to review the cases of diabetes and uveitis in the literature.

RECENT FINDINGS

The basis of an association between uveitis and diabetes mellitus (DM) is the common pathophysiology of inflammation. There are several reports on a DM-related uveitis, defined as idiopathic anterior uveitis in the presence of poorly controlled DM, but causation has not been established. There are conflicting results in the literature regarding an association between uveitis and DM. More studies are needed to determine if an association truly exists.

Genome-wide epistasis and pleiotropy characterized by the bipartite human phenotype network

Networks are central to turning the colossal amount of information generated by high-throughput genetic technology into manageable sources of knowledge. They are an intuitive way of representing interaction data, yet they offer a full set of sophisticated quantitative tools to analyze the phenomena they model. When combining genetic information, diseases, and phenotypic traits, networks can reveal and facilitate the analysis of pleiotropic and epistatic effects at the genome-wide scale. Genome-wide association study data is publicly available, and so are gene and pathway databases, and many more, making the global overview next to impossible. Networks allow information from these multiple sources to be encompassed. We use connections between the strata of the network to characterize pleiotropy and epistasis effects taking place between traits and biological pathways. The global graph-theory-based quantitative methods reveal that levels of pleiotropy and epistasis are in-line with theoretical expectations. The results of the magnified "glaucoma" region of the network confirm the existence of well-documented interactions, supported by overlapping genes and biological pathways and more obscure associations. They have the potential to generate new hypotheses for yet uncharacterized interactions. As the amount and complexity of genetic data increase, bipartite and, more generally, multipartite networks that combine human diseases and other physical attributes with layers of genetic information have the potential to become ubiquitous tools in the study of complex genetic, phenotypic interactions, and possibly improve personalized medicine.

Using the bipartite human phenotype network to reveal pleiotropy and epistasis beyond the gene

With the rapid increase in the quality and quantity of data generated by modern high-throughput sequencing techniques, there has been a need for innovative methods able to convert this tremendous amount of data into more accessible forms. Networks have been a corner stone of this movement, as they are an intuitive way of representing interaction data, yet they offer a full set of sophisticated statistical tools to analyze the phenomena they model. We propose a novel approach to reveal and analyze pleiotropic and epistatic effects at the genome-wide scale using a bipartite network composed of human diseases, phenotypic traits, and several types of predictive elements (i.e. SNPs, genes, or pathways). We take advantage of publicly available GWAS data, gene and pathway databases, and more to construct networks different levels of granularity, from common genetic variants to entire biological pathways. We use the connections between the layers of the network to approximate the pleiotropy and epistasis effects taking place between the traits and the predictive elements. The global graph-theory based quantitative methods reveal that the levels of pleiotropy and epistasis are comparable for all types of predictive element. The results of the magnified "glaucoma" region of the network demonstrate the existence of well documented interactions, supported by overlapping genes and biological pathway, and more obscure associations. As the amount and complexity of genetic data increases, bipartite, and more generally multipartite networks that combine human diseases and other physical attributes with layers of genetic information, have the potential to become ubiquitous tools in the study of complex genetic and phenotypic interactions.