OVERVIEW OF THE UTAH POPULATION DATABASE (UPDB)
The Utah Project on Exfoliation Syndrome (UPEXS) study was created to investigate associations between exfoliation syndrome (XFS) and systemic disorders or pathologies. To carry out this goal, the UPEXS study utilizes the broad resources of the UPDB. The UPDB (http://healthcare.utah.edu/huntsmancancerinstitute/research/updb/) is a unique resource (the only database of its kind in the United States and one of few in the world) that enables high-quality, health-related research to be performed from a compilation of statewide medical information, decades of state vital records, and census data on >8 million individuals residing in Utah. The UPDB is linked to the Utah genealogy, a compilation of large pedigrees extending back 3 to ≥11 generations, that represent most families in the state. These family members’ medical and health records are linked to vital records and can be used effectively to identify familial clustering of disorders, such as XFS, with comorbid diseases or health-related data. The medical record information includes comprehensive statewide medical diagnoses and data related to surgical procedures. These data include international classification of diseases (ICD)-9/10 and current procedural terminology codes from hospital discharges, ambulatory facility records, and Medicare claims data beginning in 1996. These data are linked to clinical examinations and diagnostic tests performed within the University of Utah Healthcare, a large, statewide health care system, which offers comprehensive eye services throughout the state, including the John Moran Eye Center at the University of Utah in Salt Lake City. For this project, study conduct approvals were obtained from the University of Utah Institutional Review Board and the Resource for Genetic and Epidemiologic Research (IRB 00081512).
XFS is characterized by fibrillary material that is deposited in the anterior segment of the eye and is associated with development of exfoliation glaucoma and cataract.1–4 XFS material is found widely through the body.5,6 In addition to ocular involvement, patients with XFS have deposits of characteristic material in multiple organ systems, these include the heart, brain, lungs, and skin.6,7
There is growing evidence that XFS patients have an increased risk for systemic disorders that may reflect the systemic tissue involvement of this disease. Epidemiologic studies of individuals with XFS have reported an increased risk of abdominal aortic aneurysms, cardiovascular disease, cerebrovascular disease, and hearing loss in these patients.8–11 These diseases have been hypothesized to be related based on information provided by autopsy, epidemiologic studies, and increasing knowledge related to molecular pathways that include lysyl oxidase-like 1 (LOXL1) and elastin.5–7,12
LOXL1 is a member of a family of 5 copper-dependent enzymes that oxidize primary amine substrates to reactive aldehydes.13 One function, among many, is the catalysis of lysine-derived cross-links in fibrillar collagens and elastin in the extracellular matrix (ECM).13 Systemic pathologies of particular interest, which relate to XFS, overlap with those that occur in the LOXL1 knockout mouse and other disorders in which dysregulation of the ECM, specifically pertaining to collagen and elastin metabolism, are known to play a role.12 For this reason, the UPEXS has focused on disorders that involve the ECM in general and elastin specifically, including pelvic organ prolapse (POP), atrial fibrillation (AFib), inguinal hernias, and chronic obstructive pulmonary disease. In this paper we present our results from the analysis of POP, as well as preliminary data for AFib.
POP, is a connective tissue disorder that affects women, particularly those who are postpartum. Prevalence estimates of symptomatic POP have been reported to range between 3% and 11%.14 About 11% to 19% of women with POP will require surgical intervention during their lifetimes.14 POP is believed to be associated with defects in elastin and connective tissue repair that are related to abnormalities in pathways for ECM tissue repair.15,16 Susceptibility to POP is believed to have a genetic component that may potentially be related to molecular pathways that include those that involve elastin and LOXL1.12,15,16 Liu et al,12 using the LOXL1 knockout mouse model, reported uterine and bladder prolapse in female knockout mice. UPEXS researchers, noting the association between LOXL1, ECM, and POP in the literature, explored the role of XFS in women with POP. These investigators reported that the risk of XFS in women with a history of POP approached 50%, a highly significant finding.17
Study Design and Results
This study, that utilized the UPDB, applied a 2-pronged approach, which incorporated a cross-sectional analysis in Medicare patients and a retrospective cohort study in patients in the University of Utah Healthcare system of hospitals and clinics. In substudy A, a cross-sectional analysis analyzed the records of 132,772 Utah women who were Medicare recipients for ≥3 consecutive years between 1992 and 2009. In substudy B, the longitudinal risk of an incident diagnosis of XFS from January 1, 1995 to December 31, 2014 analyzed 5130 women aged between 30 and 65 years at baseline who had been diagnosed with POP compared with 15,338 age-matched female controls with no history of POP.
The results of these studies were consistent. In substudy A, the cross-sectional analysis, the mean age of the women was 82 years (age at last year of follow-up). In these Medicare beneficiaries, it was found that POP was associated with a 56% increased risk of having a diagnosis of XFS (odds ratio, 1.56; 95% confidence interval, 1.4-1.7) In substudy B, the longitudinal analysis, the incident risk of having an XFS diagnosis was 48% greater in women aged 30 to 65 years with a diagnosis of POP compared with an age-matched female control group without a diagnosis of POP over 20 years of follow-up (hazard ratio, 1.48; 95% confidence interval, 1.1-1.9). In both studies, using different approaches, the risk of being diagnosed with XFS was increased in women with POP, a common disorder of ECM.
AFib is the most common cause of sustained cardiac arrhythmia, a major cause of morbidity and, like XFS, its prevalence increases substantially after age 50.18,19 AFib results from a complex interaction between chemical and structural changes within the atrial myocardium.19 Pathologic changes include hypertrophy, dilation, and fibrosis, which ultimately lead to chaotic electrical conduction within the atria and an irregular cardiac rhythm.18,19 In a review of autopsies performed on 30 patients (age, 64±12 y) atrial fibrosis of the ECM was correlated with AFib.20 ECM volume and composition also correlate with persistence of AFib. LOX, the first of the LOX-LOXL family members identified, is upregulated in AFib and seems to contribute to structural remodeling of cardiac tissue in patients with this disease.21 Alterations of LOXL1 enzymes may alter epithelial cells and influence a fibrogenic conversion in myofibroblasts and other muscle type cells.22,23
Transforming growth factor-β1 (TGFβ1) is a potent cytokine that plays a major role in ECM remodeling, elastosis, and fibrosis. There is growing evidence that supports a role for TGFβ1 in the pathogenesis of XFS and AFib.24–27 In ocular diseases, TGFβ1 is expressed at higher levels in the aqueous humor of eyes in patients with XFS as well as in aqueous humor from patients with XFG compared with primary open angle glaucoma.24 TGFβ1 levels are also increased in the serum of patients with XFS.25 With regard to a role in cardiac diseases, TGFβ1 has been implicated as a central regulating factor in cardiac fibrogenesis, with increased serum levels of this cytokine shown to be elevated in patients with AFib.26,27 One function of TGFβ1 is to regulate the production of ECM, inhibit degradation of ECM, and induce LOX gene expression and activity, which supports the role of this protein in XFS-associated pathology.28
The potential support for a pathogenic physiological relationship between XFS and AFib was the foundation for a preliminary study to explore the hypothesis that these 2 diseases are clinically associated. We analyzed the Medicare records of a sample population of 211,768 Utah Medicare beneficiaries who were enrolled between 1992 and 2009. Patients aged 65 and above who had ≥3 consecutive years of medical records were included. We performed an unconditional logistic regression using ICD-9 codes to define XFS (365.52 and 366.11) and an outcome of AFib (427.31), after adjusting for age and sex, to calculate the hazard ratio to estimate the risk of AFib in patients with XFS compared with those without XFS. ICD-9 codes for XFS were previously validated in a chart review and found to have high sensitivity (90.7%).29
We found that the risk of patients with XFS developing AFib was 55% greater than that of patients without XFS.30 This finding, similar to that observed in the study of POP, strongly supports an association between XFS and AFib. No difference for risk based on sex was observed. We observed an unusually high prevalence for AFib (25.8%) in the UPDB population. It is possible that the ICD-9 codes, which were not validated by chart review, may lack specificity. Although these data are preliminary and under continuing analysis, we believe the findings are of interest and provide additional support for the role of XFS in systemic disorders.
The association of XFS with systemic disorders is supported by the analysis of a robust population-based data set, the UPDB. The diagnosis of XFS, a complex inherited systemic disorder, is related to risk of XFS in women with POP. We have also observed a similar trend in a preliminary study examining the relationship of XFS with AFib. Both disorders share abnormalities in elastin and ECM metabolism. This is similar to patients with XFS, where elastin and ECM synthesis are altered or dysregulated. These data support the notion that an insult or triggering event, such as childbirth in the case of women with POP or chronic mechanical stress in AFib, is more likely to cause disease in patients with underlying genetic predisposition to XFS. These studies were conducted based on the hypothesis that connective tissue containing elastin, regulated and repaired by enzymes such as LOXL1, may be associated with XFS. These data are helping to reform our understanding of the implications of the role of XFS in systemic disorders.10,29,30 There are likely multiple genetic and environmental influences that contribute to these relationships. These include LOXL1 dysregulation that may be influenced by variants in the LOXL1 antisense gene, or environmental factors like ultraviolet light exposure.31
These studies are the first of many that will utilize this unique and robust population-based resource to continue to examine the role of XFS in nonocular systemic ECM conditions. Systemic conditions with altered ECM metabolism in addition to those discussed here, such as inguinal hernias, emphysematous lung disease, vascular diseases such as carotid artery and coronary artery diseases to name a few, may also share biological pathways with XFS. This data will continue to improve our understanding of XFS-related systemic disorders and, in so doing, will provide a unique perspective to diagnosis, management, and treatment.
1. Ritch R. Exfoliation syndrome
: the most common identifiable cause of open-angle glaucoma. J Glaucoma. 1994;3:176–177.
2. Kang JH, Loomis S, Wiggs JL, et al. Demographic and geographic features of exfoliation glaucoma in 2 United States-based prospective cohorts. Ophthalmology. 2012;119:27–35.
3. Whigham BT, Allingham RR. Review: the role of LOXL1
in exfoliation syndrome
/glaucoma. Saudi J Ophthalmol. 2011;5:347–352.
4. Thorleifsson G, Magnusson KP, Sulem P, et al. Common sequence variants in the LOXL1
gene confer susceptibility to exfoliation glaucoma. Science. 2007;317:1397–1400.
5. Schlötzer-Schrehardt U, Naumann GO. Ocular and systemic pseudoexfoliation syndrome. Am J Ophthalmol. 2006;141:921–937.
6. Schlötzer-Schrehardt U, Pasutto F, Sommer P, et al. Genotype-correlated expression of lysyl oxidase-like 1 in ocular tissues of patients with pseudoexfoliation syndrome/glaucoma and normal patients. Am J Pathol. 2008;173:1724–1735.
7. Streeten BW, Li ZY, Wallace RN, et al. Pseudoexfoliative fibrillopathy in visceral organs of a patient with pseudoexfoliation syndrome. Arch Ophthalmol. 1992;110:1757–1762.
8. Djordjevic-Jocic J, Jovanovic P, Bozic M, et al. Prevalence and early detection of abdominal aortic aneurysm in pseudoexfoliation syndrome and pseudoexfoliation glaucoma. Curr Eye Res. 2012;37:617–623.
9. Ritch R, Schlötzer-Schrehardt U. Exfoliation (pseudoexfoliation) syndrome: toward a new understanding. Proceedings of the First International Think Tank. Acta Ophthalmol Scand. 2001;79:213–217.
10. Bettis DI, Allingham RR, Wirostko BM. Systemic diseases associated with exfoliation syndrome
. Int Ophthalmol Clin. 2014;54:15–28.
11. Mitchell P, Wang JJ, Smith W. Association of pseudoexfoliation syndrome with increased vascular risk. Am J Ophthalmol. 1997;124:685–687.
12. Liu X, Zhao Y, Gao J, et al. Elastic fiber homeostasis requires lysyl oxidase-like 1 protein. Nat Genet. 2004;36:178–182.
13. Mäki JM. Lysyl oxidases in mammalian development and certain pathological conditions. Histol Histopathol. 2009;24:651–660.
14. Wu JM, Vaughan CP, Goode PS, et al. Prevalence and trends of symptomatic pelvic floor disorders in US women. Obstet Gynecol. 2014;123:141–148.
15. Liu X, Zhao Y, Pawlyk B, et al. Failure of elastic fiber homeostasis leads to pelvic floor disorder. Am J Pathol. 2006;168:519–528.
16. Couri BM, Boraziani A, Lenis AT, et al. Validation of genetically matched wild-type strain and lysyl oxidase-like 1 knockout mouse model of pelvic organ prolapse
. Female Pelvic Med Reconstr Surg. 2014;20:287–292.
17. Wirostko BM, Curtin K, Ritch R, et al. Risk for exfoliation syndrome
in women with pelvic organ prolapse
: a Utah Project on Exfoliation Syndrome
(UPEXS) Study. JAMA Ophthalmol. 2016;134:1255–1262.
18. Allessie MA, Boyden PA, Cammetal AJ. Pathophysiology and prevention of atrial fibrillation
. Circulation. 2001;103:769–777.
19. Kannel WB, Wolf PA, Benjamin EJ, et al. Prevalence, incidence, prognosis, and predisposing conditions for atrial fibrillation
: population-based estimates. Am J Cardiol. 1998;82 (8A):2N–9N.
20. Platonov PG, Mitrofanova LB, Orshanskaya V, et al. Structural abnormalities in atrial walls are associated with presence and persistency of atrial fibrillation
but not with age. J Am Coll Cardiol. 2011;58:2225–2232.
21. Adam O, Theobald K, Lavall D, et al. Increased lysyl oxidase expression and collagen cross-linking during atrial fibrillation
. J Mol Cell Cardiol. 2011;50:678–685.
22. Diaz R, Kim JW, Hui JJ, et al. Evidence for the epithelial to mesenchymal transition in biliary atresia fibrosis. Hum Pathol. 2008;39:102–115.
23. Laczko R, Szauter KM, Csiszar K. LOXL1
-associated candidate epithelial pathomechanisms in exfoliation glaucoma. J Glaucoma. 2014;23 (suppl 1):S43–S47.
24. Koliakos GG, Schlötzer-Schrehardt U, Konstas AG, et al. Transforming and insulin-like growth factors in the aqueous humour of patients with exfoliation syndrome
. Graefes Arch Clin Exp Ophthalmol. 2001;239:482–487.
25. Schlötzer-Schrehardt U, Zenkel M, Küchle M, et al. Role of transforming growth factor-β1 and its latent form binding protein in pseudoexfoliation syndrome. Exp Eye Res. 2001;73:765–780.
26. Lijnen PJ, Petrov VV, Fagard RH. Induction of cardiac fibrosis by transforming growth factor-β 1. Mol Gen Metabol. 2000;71:418–435.
27. Seko Y, Nishimura H, Takahashi N, et al. Serum levels of vascular endothelial growth factor and transforming growth factor-beta 1 in patients with atrial fibrillation
undergoing defibrillation therapy. Jpn Heart J. 2000;41:27–32.
28. Hinz B. The extracellular matrix and transforming growth factor-β1: tale of a strained relationship. Matrix Biol. 2015;47:54–65.
29. Wirostko BM, Christiansen SM, Schaumberg D, et al. High risk pseudoexfoliative families identified in the Utah population database. Poster presented at: Annual Meeting of the Association for Research in Vision and Ophthalmology, Orlando, FL, May 2014.
30. Fields T, Curtin K, Hageman GS, et al. Exfoliation syndrome
is associated with increased risk of atrial fibrillation
. Poster presented at the American Glaucoma Society, California, March 2015.
31. Hauser MA, Aboobakar IF, Lui Y, et al. Genetic variants and cellular stressors associated with exfoliation syndrome
modulate promoter activity of a IncRNA within the LOXL1
locus. Hum Mol Genet. 2015;24:6552–6563.