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Journal of Crohn's and Colitis (2014) 8, 513–520

Total soluble and endogenous secretoryreceptor for advanced glycation endproducts(RAGE) in IBD

Berrie Meijer a,b, Teagan Hoskin c, Anna Ashcroft c, Laura Burgess b,Jacqueline I. Keenand, James Falveyc,e,Richard B. Gearryc,e, Andrew S. Dayb,f,⁎

a Department of Gastroenterology, Academic Medical Center, Amsterdam, The Netherlandsb Department of Paediatrics, University of Otago, Christchurch, New Zealandc Department of Medicine, University of Otago, Christchurch, New Zealandd Department of Surgery, University of Otago, Christchurch, New Zealande Department of Gastroenterology, Christchurch Hospital, Christchurch, New Zealandf Department of Paediatrics, Christchurch Hospital, Christchurch, New Zealand

Received 28 June 2012; received in revised form 6 November 2013; accepted 6 November 2013

Non-standard abbreviations: RAGE,colitis activity index; SES-CD, Simple e⁎ Corresponding author at: Departme

Tel.: +64 3 3640747; fax: +64 3 36409E-mail address: andrew.day@otago

1873-9946/$ - see front matter © 2013http://dx.doi.org/10.1016/j.crohns.20

KEYWORDSSoluble receptorfor advanced glycationendproducts (sRAGE);Endogenous secretoryRAGE (esRAGE);C-reactive protein (CRP);Endoscopic activity;Inflammatory boweldisease;Enzyme-linkedimmunosorbent assay

Abstract

Background and aims: Recruitment and activation of neutrophils, with release of specificproteins such as S100 proteins, is a feature of inflammatory bowel disease (IBD). Soluble forms ofthe receptor for advanced glycation endproducts (sRAGE), and variants such as endogenoussecretory (esRAGE), can act as decoy receptors by binding ligands, including S100A12. The aimsof this study were to determine total sRAGE and esRAGE concentrations in patients with IBD andcorrelate these with C-reactive protein (CRP), endoscopic scores and clinical disease activityscores.Methods: EDTA-plasma was collected from patients undergoing colonoscopy including thosewith Crohn's disease (CD: n = 125), ulcerative colitis (UC: n = 79) and control patients withoutendoscopic signs of inflammation (non-IBD: n = 156). Concentrations of sRAGE and esRAGE weredetermined by enzyme-linked immunosorbent assay and plasma CRP concentrations measured.

Standard clinical disease activity and endoscopic severity scores were defined for all subjects.Results: Plasma sRAGE concentrations were lower in UC (but not CD) than non-IBD subjects(p b 0.01). Whilst sRAGE concentrations correlated negatively with endoscopic activity in UC(p b 0.05), this was not seen in CD. In contrast, esRAGE correlated negatively with disease

Receptor for advanced glycation end-products; HBI, Harvey–Bradshaw index; SCCAI, Simple clinicalndoscopic score for Crohn's disease.nt of Paediatrics, University of Otago, Christchurch, P.O. Box 4345, Christchurch 8140, New Zealand.19..ac.nz (A.S. Day).

European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.13.11.004

514 B. Meijer et al.

activity in both UC (p = 0.002) and CD (p = 0.0001). Furthermore, sRAGE and esRAGE concentrationscorrelated inversely with CRP values (p b 0.0001).Conclusions: Although total sRAGE varied with activity in UC, esRAGE concentrations correlatedinversely with endoscopic disease activity and CRP levels in both UC and CD. Additional studiesare required to further define the significance of sRAGE and esRAGE in IBD.© 2013 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.

1. Introduction

Crohn's disease (CD) and ulcerative colitis (UC), collectivelyknown as inflammatory bowel disease (IBD), are chronicincurable inflammatory conditions involving the gastrointes-tinal tract that result in significant morbidity and high ratesof hospital admission.1,2 The diagnosis of IBD relies uponhistological examination of mucosal biopsies obtained endo-scopically.3 For example, ileocolonoscopy, a relatively invasiveand expensive investigation, is currently undertaken to confirmor exclude IBD in individuals with suggestive symptoms.4

Over recent years, researchers have been searching for sen-sitive and specific non-invasive biomarkers that may distinguishIBD from non-inflammatory conditions, such as irritable bowelsyndrome (IBS).5–10 Studies evaluating serum and faecal levelsof one such biomarker, S100A12, have shown promisingresults.11,12 S100A12, also known as EN-RAGE (ExtracellularNewly identified Receptor for Advanced Glycation Endproductsbinding protein) or Calgranulin C, is a pro-inflammatory proteinpredominantly secreted by neutrophils.9,13 S100A12 is thoughtto bind RAGE (Receptor for Advanced Glycation End-products),resulting in the activation of intracellular signalling cascadesand the production and release of proinflammatory cytokines(e.g. tumour necrosis factor (TNF)-α and interleukin (IL)-1β)that are linked to IBD pathogenesis.14

In addition to membrane-bound RAGE, soluble forms ofthis receptor (sRAGE) are now recognised. These circulatingproteins may act as decoys, thereby preventing binding ofligands with membrane-bound RAGE.15–17 Accordingly, onewould hypothesise that levels of sRAGE would decrease insettings of active inflammation associated with increasedproduction of S100A12 consequent to increased binding ofsRAGE with S100A12. sRAGE negatively correlates with diseaseseverity in various systemic conditions, such as coronary arterydisease,18 systemic lupus erythematosus,19 atherosclerosis20

and juvenile idiopathic arthritis.21 However, imbalance be-tween S100A12 and sRAGE could also lead to uninterruptedS100A12 activity.

The total pool of sRAGE includes ectodomain-shed RAGEand a C-terminally truncated variant known as endogenoussecretory (es) RAGE, which is secreted extracellularly.19,20

By acting as a decoy receptor, esRAGE is able to neutralisethe actions of advanced glycation endproducts (AGEs) includingS100A12.22,23 Thus, the measurement of circulating esRAGElevels rather total sRAGE levels may prove a more biologicallyrelevant, and more sensitive, biomarker of disease activity inpatients with IBD.

To date, the patterns of circulating sRAGE have beenevaluated in just three studies of patients with IBD. Norelationship between disease activity of IBD and sRAGE levelswas demonstrated in two studies,6,24 whereas increased levelsof sRAGE were shown in one study of 60 individuals with UC.25

However, circulating levels of esRAGE have not yet beendefined in the context of IBD. Thus, the aim of thisobservational study was to determine sRAGE and esRAGEconcentrations in patients with endoscopically confirmedestablished or newly diagnosed IBD and correlate theseresults with endoscopic disease activity, clinical diseaseactivity and plasma CRP concentration.

2. Materials and methods

2.1. Participants

All patients undergoing colonoscopy to diagnose, evaluate orexclude IBD in 2010–2011 at the Department of Gastroen-terology, Christchurch Hospital, Christchurch, New Zealandwere invited to participate in this study. Informed consentwas obtained from all patients or caregivers. The study wasapproved by the Upper South A Regional Ethics Committee.

The study group comprised patients with known or newlydiagnosed CD or UC, based on standard endoscopic, histologicalor radiological criteria.3 The non-IBD control group comprisedpatients in whom IBD was suspected on clinical grounds, but noevidence of bowel inflammation at colonoscopy or subsequentinvestigations was found. Patients with other gastrointestinalpathology, such as IBD unclassified (IBDU), colorectal polyps andcolorectal cancer were excluded from the non-IBD controlgroup.

Baseline demographic data including age, gender, currentmedical therapy and details of known gastrointestinal diseasewere collected at enrolment. GI symptoms in the week prior tocolonoscopy were recorded.

2.2. Disease assessment

Disease activity was measured using a range of indices. Clinicaldisease indices included the Harvey Bradshaw index (HBI) forCD26 and the simple clinical colitis activity index (SCCAI) forUC.27 Mucosal scores were assessed using the Simple EndoscopicScore for Crohn's Disease (SES-CD)28 and the Rachmilewitz scorefor UC.29 For those with UC, inflammation was classified asinactive (score 0–3),mild (score 4–6),moderate (score 7–9) orsevere (score 10–12) disease, as described previously.30 Forthose with CD, SES-CD scores were defined as inactive (score0–2), mild (score 3–6), moderate7–15 or severe (score ≥16).31

2.3. Sample collection

Venous blood samples were collected in 4 ml EDTA-tubesprior to colonoscopy. After storage at 4 °C overnight, sampleswere centrifuged for 5 min at 2500 rpm. Plasma was collected

Table 1 Clinical characteristics of CD, UC and non-IBD patients according to endoscopic severity scores.

UC CD non-IBD

N (%) N (%) N (%)

Total 79 125 156

Male 44 (55.7) 62 (49.6) 55 (35.3)Age (years), mean ± SD 53.5 ± 14.4 44.6 ± 15.1 36.9 ± 18.7Newly diagnosed 7 (8.9) 20 (16.0) –Disease activity (endoscopic scores a)

Inactive 50 (63.3) 55 (44.0) –Mild 16 (20.2) 42 (33.6) –Moderate 9 (11.4) 17 (13.6) –Severe 4 (5.1) 11 (8.8) –

Disease activity (HBI)≤5 – 71 (56.8) –5–10 – 36 (28.8) –11–19 – 16 (12.8) –≥20 – 2 (1.6) –

Disease activity (SCCAI)≤5 64 (81.0) – –6–10 11 (13.9) – –N10 4 (5.1) – –

Disease location (CD)Ileitis – 60 (48.0) –Colitis – 34 (27.2) –Ileocolitis – 31 (24.8) –

Disease extent (UC)Proctitis 13 (16.5) – –Left-sided colitis 35 (44.3) – –Pancolitis 31 (39.2) – –

Abbreviations: IBD, inflammatory bowel disease; CD, Crohn's disease; UC, ulcerative colitis; HBI, Harvey–Bradshaw index.22; SCCAI, simpleclinical colitis activity index.23a Rachmilewitz index25 for ulcerative colitis, simple endoscopic score for Crohn's disease (SES-CD).24

515Plasma sRAGE and esRAGE in IBD

in 1.7 ml Eppendorf tubes and stored at −80 °C until used foranalysis.

In addition, faecal samples were obtained prior to colonos-copy and stored at −80 °C and biopsies of inflamed andnon-inflamed small and large intestine were taken duringcolonoscopy for histological examination and RNA expressionanalysis, although they were not used in the current study.

2.4. Measurement of plasma sRAGE, esRAGEand CRP

Plasma sRAGE and esRAGE concentrations were measuredusing commercial enzyme-linked immunosorbent assay (ELISA)kits (R&D Systems, Minneapolis, MA, USA and B-BridgeInternational, Inc. Cupertino, CA, USA, respectively) followingthe manufacturer's instructions.6 Optical density was measuredusing an ELISA plate reader (Spectramax 190, MolecularDevices, Sunnyvale, CA, USA). Plasma concentrations of thetwo proteins were calculated using SoftMax Pro (version5.3, October 1998; Molecular Devices, Sunnyvale, CA, USA).The lower detection limit of the sRAGE ELISA was 78 pg/ml,whereas the esRAGE assay detected 50 pg/ml. Results outsidethe standard range were repeated in higher or lower dilutionsrespectively.

CRP was measured using a standard analyser (AbbottC8000, Libertyville, IL, USA) after vigorous shaking andcentrifuging of the tubes at 13000 rpm for one minute.

2.5. Statistical analysis

Data was analysed using SPSS 20.0 (SPSS Inc., Chicago,IL, USA) and GraphPad Prism 5.0c (GraphPad Inc., San Diego,CA, USA). Mann–Whitney U-tests were used to compare sRAGEand esRAGE concentrations between inactive, mild, moderateand severely active mucosal inflammation. Spearman's corre-lation was used to determine correlation coefficients andsignificance. Results are presented as mean ± standard errorof the mean (SEM), unless otherwise specified. Normal prob-ability plot and histograms of raw data showed violation ofnormality and thus the appropriate non-parametric testswere used. The level of significance was set as a two-tailedp b 0.05.

3. Results

3.1. Patient characteristics

The study group comprised 125 patients (3 children) withestablished or newly diagnosed CD and 79 patients withestablished or newly diagnosed UC. The remaining cohortconsisted of 254 patients, of which 156 (23 children) wereincluded as non-IBD controls. Excluded were patients withsignificant intestinal pathology, other than inflammation(e.g. polyps and cancer). Patient baseline characteristics didnot differ between groups (Table 1).

Non-IBD CD UC

IBD

0

25

50

75

100

125 p<0.0001

p<0.01p<0.0001

A

CR

P (

mg

/L)

125 p<0.0001

B

516 B. Meijer et al.

3.2. Plasma C-reactive protein concentrations

Plasma CRP concentrations were higher in IBD (12.5 ±1.98 mg/l; p b 0.0001), CD (13.3 ± 2.1 mg/l; p b 0.0001)and UC (11.2 ± 3.94 mg/l; p b 0.001) than non-IBD controls(5.31 ± 1 mg/l). Within the CD group, CRP was higher in thosewith moderate (20.7 ± 4.47 mg/l; p b 0.001) and severe(45.2 ± 12.9 mg/l; p b 0.0001) endoscopic inflammation,than in the inactive group (6.27 ± 1.2 mg/l). However, CRPvalues were not elevated in mildly active disease (11.22 ±3.73 mg/l; p = 0.06) compared to those with inactive disease.Within the UC group, higher concentrations of CRP wereseen in patients with moderate (41.3 ± 31.5 mg/l; p b 0.01)and severe (11.2 ± 3 mg/l; p b 0.05) endoscopic inflammation,than in those with inactive disease (4.18 ± 0.6 mg/l). Again,those with mild disease did not have higher CRP concentrationsthan those with inactive disease (16.1 ± 7.1 mg/l; p = 0.168)(Fig. 1A–C).

Inac

tive

Mild

Moderat

e

Sever

e

0

25

50

75

100

p<0.01p=0.06

CR

P (

mg

/L)

200

300

C

3.3. Plasma soluble RAGE concentrations

Plasma sRAGE concentrations were lower in UC than non-IBDcontrols (1173 ± 68.2 pg/ml vs 1455 ± 62 pg/ml: p b 0.01).However, sRAGE concentrations in CD (1447 ± 72 pg/ml) orIBD (1341 ± 52 pg/ml) were not different to non-IBD controlvalues (p N 0.05 for both comparisons). Within the UC group,sRAGE concentrations were lower in severe (616 ± 85 pg/ml)compared with inactive (1276 ± 89 pg/ml) endoscopic in-flammation (p b 0.05). Differences between mild (p = 0.32)and moderate (p = 0.12) endoscopic inflammation did notdiffer from that of the inactive group. In contrast, nodifferences were found between those with mild (p = 0.20),moderate (p = 0.46) or severe endoscopic CD (p = 0.10) andthose with inactive disease (Fig. 2A and B).

Inac

tive

Mild

Moderat

e

Sever

e

0

20

40

60

80

100 p<0.05p<0.05

p=0.168

CR

P (

mg

/L)

3.4. Plasma endogenous secretoryRAGE concentrations

In contrast to the findings for sRAGE, esRAGE concentrationsdiffered between UC, CD and the control group (Fig. 3A).In the CD cohort, esRAGE concentrations were highest inthose with inactive disease (449.3 ± 24.95 pg/ml) and lowestin those with severe disease activity (181.8 ± 23.11 pg/ml,p b 0.0001; Fig. 3B). Furthermore, concentrations of esRAGEwere also lower in patients with active UC (83.5 ± 14.1 pg/ml)compared to those in remission (402.0 ± 30.7 pg/ml, p =0.001; Fig. 3C).

Figure 1 Plasma CRP in patients with and without inflamma-tory bowel disease. CRP was elevated in Crohn's disease,ulcerative colitis and in the combined IBD group compared tocontrol subjects without IBD (A). In both CD (B) and UC (C), CRPvalues increased with disease severity.

3.5. Relationship between esRAGE and sRAGE

In the UC and CD cohorts, the percent contribution of esRAGElevels to the total circulating RAGE concentration (sRAGE) wasdefined for each level of disease activity. The contribution ofesRAGE to the total sRAGE varied in a disease activitydependent fashion for both UC (inactive 33.0 ± 1.78%; mild23.2 ± 2.11%; moderate 22.6 ± 2.38% and severe 13.5 ± 0.75%;p = 0.0004) and CD (inactive 32.3 ± 1.68%; mild 26.4 ± 1.37%;moderate 24.8 ± 3.50% and severe 14.9 ± 1.26%; p = 0.0002)(Fig. 4 A and B).

3.6. Correlation between disease markers

The Harvey–Bradshaw index (HBI) scores correlated withthe endoscopic disease activity scores(r = 0.227, p b 0.05) inthe patients with CD, as did CRP (r = 0.393; p b 0.0001)(Table 2). In contrast, there was no correlation between

Inac

tive

Mild

Moderat

e

Sever

e0

1000

2000

3000

4000

5000

AP

lasm

a sR

AG

E (

pg

/ml)

Inac

tive

Mild

Moderat

e

Sever

e0

500

1000

1500

2000

2500

3000

B

p<0.05

Pla

sma

sRA

GE

(p

g/m

l)

Figure 2 Plasma sRAGE concentrations in 204 patients withinflammatory bowel disease. sRAGE concentrations did not differ(p N 0.05) according to disease activity in 125 subjects with Crohn'sdisease (A). However, sRAGE did vary according to disease severityin 79 individuals with ulcerative colitis, with lower levels in thosewith severe disease (p b 0.05) (B).

inacti

ve mild

mod

erat

e

seve

re0

200

400

600

800

1000p<0.0001

p=0.0043

p=0.0085A

Pla

sma

esR

AG

E (

pg/m

l)

inacti

ve mild

mod

erat

e

seve

re0

200

400

600

800

1000

2000p=0.001

p=0.0038p=0.0035

p=0.039

B

Pla

sma

esR

AG

E (

pg/m

l)

Figure 3 Plasma esRAGE concentrations in 204 patients withinflammatory bowel disease. esRAGE, measured in plasma,showed a disease-activity dependent decrease in individualswith CD (A) and those with UC (B).

517Plasma sRAGE and esRAGE in IBD

sRAGE concentrations and endoscopic activity (p = 0.97).However, there was a weak negative correlation betweenesRAGE and endoscopic disease activity (r = −0.2356;p b 0.01).

In patients with UC, the simple clinical colitis activityindex (SCCAI) correlated with endoscopic disease activity(r = 0.343, p b 0.01) (Table 3). Correlations between CRPand endoscopic activity (r = 0.384; p b 0.001) and betweensRAGE (r = −0.231; p b 0.05) and endoscopic activity werealso evident. In addition, there was a moderate negativecorrelation between esRAGE and the Rachmilewitz index(r = −0.4220; p b0.0001) (Table 3).

There was a negative correlation between CRP and bothsRAGE and esRAGE in the total study group (r = −0.251 andr = −0.249 respectively, both p b 0.0001).

4. Discussion

The current study demonstrated a significant relationshipbetween circulating RAGE and disease activity in IBD, especiallyfor the endogenous secretory variant of this protein. Although

total sRAGE values correlated inversely with endoscopic diseaseactivity in UC, esRAGE values correlated with disease activity inboth UC and CD. In addition, CRP values were negativelycorrelated with total sRAGE concentrations in patients with IBDand controls. These data suggest that RAGE production andconsumption may contribute to the complex inflammatoryevents seen in IBD.

This is the first study describing the relationship betweensRAGE concentration and endoscopic disease activity in IBD.To date, three other studies describe the patterns of sRAGEin IBD. In 2007, Leach et al.6 determined serum sRAGEconcentrations in 39 children with IBD. sRAGE concentra-tions in this group did not differ from those in the non-IBDcontrols (median 1661 [range 555–3613] pg/ml vs 2001[777–2915] pg/ml), or between CD, UC and IBD. The study byLeach and colleagues6 differs from the current study in thatit included solely paediatric patients at the time of diagnosisof IBD and included a smaller number of subjects.

Malickova et al.24 measured serum sRAGE concentrationsin 29 adult patients with long-standing IBD prior to biologicaltreatment and compared these to the levels in gender andage-matched control serum samples from 30 healthy blooddonors. Again, there was no difference between IBD patientsand healthy donors (mean ± SD; 772 ± 274 pg/ml vs 720 ±107 pg/ml, respectively, p = 0.159). Three-quarters of the

inacti

ve mild

mod

erat

e

seve

re0

20

40

60

80

100p=0.0001

p=0.0002

p=0.0215p=0.0453

A

esR

AG

E/s

RA

GE

(%

)

inacti

ve mild

mod

erat

e

seve

re0

20

40

60

80

100p=0.001

p=0.0384

p=0.0112

p=0.0101p=0.0046

B

esR

AG

E/s

RA

GE

(%

)

Figure 4 The relationship between esRAGE and sRAGE inpatientswith CD andUC. The percentage contributions ofmeasuredesRAGE to the total sRAGE were calculated in individuals with CD(A) and UC (B), according to disease activity scores.

518 B. Meijer et al.

patients in this study were diagnosed with CD. These dataare consistent with the findings seen in the CD population inthe current study, together suggesting that variations insRAGE concentrations may be less relevant in CD than in thesetting of UC.

The most recent study investigating total sRAGE concen-trations in IBD included 60 adult patients with UC.25 Increasedserum sRAGEwas seen in this group, in comparison to a group of113 healthy controls (median [interquartile range]; 740 [640–820] pg/ml vs 580 [470–770] pg/ml, respectively, p b 0.05).The differences between the findings in this Turkish studyand those seen in the UC cohort included in the current studymay be explained by methodological differences, includingthe ELISA kits utilised and variations in the control groups.Furthermore, ethnic differences may also be relevant. A recent

Table 2 Correlation of the simple endoscopic score for Crohn's dise

Endoscopic activity a Inactive (0–3) Mild (4

No. of patients 55 42HBI 4.55 ± 0.59 4.14 ±sRAGE (pg/ml) 1616 ± 122.4 1310 ±esRAGE (pg/ml) 449.3 ± 24.95 340.7 ±CRP (mg/l) 6.27 ± 1.18 11.22 ±

Abbreviations: HBI, Harvey Bradshaw index22; CRP, C-reactive protein;esRAGE, endogenous secretory RAGE.Numbers are presented as mean ± SEM.a Activity scored by the simple endoscopic score for Crohn's Disease

study showed wide variations in sRAGE expression acrossdifferent ethnic groups.32

The patterns of sRAGE expression have previously beendefined in several other inflammatory states. For instance,much lower levels of sRAGE were seen in a group of childrenwith Kawasaki's disease (an acute vasculitis with potentiallong-term cardiac complications) than in a control group ofchildren.33 This finding was seen despite very elevated levels ofS100A12 in the children with Kawasaki's disease, suggesting animbalance between S100A12 and sRAGE. The relationshipbetween sRAGE and S100A12 was also determined in a groupof adults with end-stage renal disease.20 Levels of sRAGEnegatively correlated with several key vascular findings inthis study, with inverse relationships to S100A12 levels. Inaddition, lower levels of sRAGE are associated with increasedseverity of chronic lung disease in adults34 and increased risk ofsepsis in preterm infants.35

Most of these studies, including the current study, evaluatedplasma sRAGE concentrations rather than serum levels. Theimpact of this is not clear at present. The collection methoddoes, however, affect themeasurement of S100A12,36 meaningthat concurrent measurement of S100A12 was not possible inthe current study.

esRAGE concentrations have been assessed in several otherdisease states, such as vascular disease and diabetes.23,37–39

Low levels of esRAGE are associated with increased risk ofdeveloping renal complications in individuals with Type 1Diabetes.37 Furthermore, strong correlations between esRAGEand oxidative stress have been established in Type 2 Diabetes.38

One study evaluated esRAGE mRNA levels in peripheral bloodmononuclear cells in a small group of 13 patients with CD.39 Thisstudy focused upon esRAGE expression in a larger group ofindividuals with joint disease and included the subjects with CDas a disease control group. esRAGE expression was down-regulated in CD (76%) compared to healthy controls (100%), butnot to the same level seen in the patients with joint disease(54%). Levels of esRAGE protein were not measured in thisstudy.

The current study describes the patterns of sRAGE in thelargest group of patients with IBD and non-inflammatorycontrols to date, and provides the first observations ofchanges in esRAGE concentrations in IBD. A further strengthof the current study is that endoscopic activity is used as areference, instead of clinical disease scores as used in otherstudies. Clinical disease scores may not always reflect endo-scopic inflammation due to the presence of non-inflammatorysymptoms in many patients. Although a large number ofpatients were included, the smaller sizes of sub-groups with

ase (SES-CD) subgroups with the HBI, plasma sRAGE and CRP.

–6) Moderate (7–9) Severe (10–12)

17 110.66 7.53 ± 1.69 7.73 ± 0.9492.6 1438 ± 241.9 1133 ± 150.526.64 333.4 ± 54.65 181.8 ± 23.113.73 20.74 ± 4.72 45.17 ± 12.9

sRAGE, soluble receptor for advanced glycation endproducts;

(SES-CD).24

Table 3 Correlation of the Rachmilewitz index for ulcerative colitis with the SCCAI, plasma sRAGE and CRP.

Endoscopic activity a Inactive (0–3) Mild (4–6) Moderate (7–9) Severe (10–12)

No. of patients 50 16 9 4SCCAI 2.24 ± 0.31 4.63 ± 0.92 5.33 ± 1.46 5.00 ± 1.47sRAGE (pg/ml) 1276 ± 89.4 1117 ± 145.7 948.4 ± 149.3 616.2 ± 84.8esRAGE (pg/ml) 402.0 ± 30.7 311.1 ± 31.7 218.6 ± 36.1 83.5 ± 14.1CRP (mg/l) 4.18 ± 0.64 16.1 ± 7.12 41.3 ± 31.47 11.23 ± 3.00

Abbreviations: SCCAI, simple clinical colitis activity index23; CRP, C-reactive protein; sRAGE, soluble receptor for advanced glycationendproducts; esRAGE, endogenous secretory RAGE.Numbers are presented as mean ± SEM.a Activity scored by the Rachmilewitz index for ulcerative colitis.25

519Plasma sRAGE and esRAGE in IBD

moderate and severe disease activity limited further analysis. Inaddition, the current study was not able to measure levels ofRAGE ligands, such as S100A12, in this population.

In conclusion, the current study has demonstrated diseaseactivity dependent variations of esRAGE in UC and CD, whilstalso showing a similar relationship for total sRAGE in the UCcohort alone. These data indicate either consumption ofesRAGE or decreased systemic production in the context ofthis chronic gut disease. Currently available evidence does notindicate that measurement of circulating RAGE would permitone to distinguish between IBD and non-inflammatory condi-tions in patients with gastrointestinal symptoms. However, thecurrent study supports esRAGE as a marker of disease activity inthe context of IBD. Further studies are now required tosubstantiate these findings and to elucidate the further clinicalroles of sRAGE and esRAGE (and related ligands) in IBD.

Statement of author contributions

BMcarried out the analysis of samples, performed the statisticalanalyses and prepared the first draft of the manuscript. LBcompleted further sample analyses, performed statisticalanalyses and contributed to the preparation of the manuscript.RG and AD conceived the studies, and participated in its designand coordination and contributed to preparation and drafting ofthe manuscript. JK participated in the sample analyses. JFperformed endoscopic scoring for all patients. TH and AAcontributed to patient recruitment, sample collection and dataanalyses. All authors read and approved the final manuscript.

Conflict of interest

None of the authors have any conflicts of interest.

Acknowledgements

The authors wish to thank the nurses and gastroenterologistsfrom the Department of Gastroenterology, ChristchurchHospital, Canterbury District Health Board, Christchurch,New Zealand for their participation in recruiting patientsand collecting samples. Thanks also to James Yeo.

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