Whole-genome sequencing of African Americans implicates differential genetic architecture in inflammatory bowel disease.

Whether or not populations diverge with respect to the genetic contribution to risk of specific complex diseases is relevant to understanding the evolution of susceptibility and origins of health disparities. Here, we describe a large-scale whole-genome sequencing study of inflammatory bowel disease encompassing 1,774 affected individuals and 1,644 healthy control Americans with African ancestry (African Americans). Although no new loci for inflammatory bowel disease are discovered at genome-wide significance levels, we identify numerous instances of differential effect sizes in combination with divergent allele frequencies. For example, the major effect at PTGER4 fine maps to a single credible interval of 22 SNPs corresponding to one of four independent associations at the locus in European ancestry individuals but with an elevated odds ratio for Crohn disease in African Americans. A rare variant aggregate analysis implicates Ca2+-binding neuro-immunomodulator CALB2 in ulcerative colitis. Highly significant overall overlap of common variant risk for inflammatory bowel disease susceptibility between individuals with African and European ancestries was observed, with 41 of 241 previously known lead variants replicated and overall correlations in effect sizes of 0.68 for combined inflammatory bowel disease. Nevertheless, subtle differences influence the performance of polygenic risk scores, and we show that ancestry-appropriate weights significantly improve polygenic prediction in the highest percentiles of risk. The median amount of variance explained per locus remains the same in African and European cohorts, providing evidence for compensation of effect sizes as allele frequencies diverge, as expected under a highly polygenic model of disease.

Mitochondrial dysfunction during loss of prohibitin 1 triggers Paneth cell defects and ileitis.

OBJECTIVE: Although perturbations in mitochondrial function and structure have been described in the intestinal epithelium of Crohn's disease and ulcerative colitis patients, the role of epithelial mitochondrial stress in the pathophysiology of inflammatory bowel diseases (IBD) is not well elucidated. Prohibitin 1 (PHB1), a major component protein of the inner mitochondrial membrane crucial for optimal respiratory chain assembly and function, is decreased during IBD. DESIGN: Male and female mice with inducible intestinal epithelial cell deletion of Phb1 (Phb1iΔIEC ) or Paneth cell-specific deletion of Phb1 (Phb1ΔPC ) and Phb1fl/fl control mice were housed up to 20 weeks to characterise the impact of PHB1 deletion on intestinal homeostasis. To suppress mitochondrial reactive oxygen species, a mitochondrial-targeted antioxidant, Mito-Tempo, was administered. To examine epithelial cell-intrinsic responses, intestinal enteroids were generated from crypts of Phb1iΔIEC or Phb1ΔPC mice. RESULTS: Phb1iΔIEC mice exhibited spontaneous ileal inflammation that was preceded by mitochondrial dysfunction in all IECs and early abnormalities in Paneth cells. Mito-Tempo ameliorated mitochondrial dysfunction, Paneth cell abnormalities and ileitis in Phb1iΔIEC ileum. Deletion of Phb1 specifically in Paneth cells (Phb1ΔPC ) was sufficient to cause ileitis. Intestinal enteroids generated from crypts of Phb1iΔIEC or Phb1ΔPC mice exhibited decreased viability and Paneth cell defects that were improved by Mito-Tempo. CONCLUSION: Our results identify Paneth cells as highly susceptible to mitochondrial dysfunction and central to the pathogenesis of ileitis, with translational implications for the subset of Crohn's disease patients exhibiting Paneth cell defects.

Maneuvering Clinical Pathways for Ulcerative Colitis.

PURPOSE OF REVIEW: Recent years have brought about several advances in the treatment of patients with ulcerative colitis (UC). Here, we discuss salient recommendations of recent treatment guidelines; review the efficacy, safety, and real-world data of vedolizumab and tofacitinib; appraise their place vis-à-vis established agents; and consider the newly proposed approaches of risk-stratified and treat-to-target therapy. RECENT FINDINGS: Once daily oral mesalamine dosing is equivalent to split dosing in mild-moderate UC. Real-world data are accumulating on the effectiveness and safety of vedolizumab for moderate to severe UC, while there are few such data on the most recently approved agent, tofacitinib. High-dose infliximab is being investigated for severe UC. New approaches are challenging the established paradigm of selecting therapy based on current disease activity. The risk-stratified approach incorporates long-term risk as well as the current burden of inflammation. The treat-to-target approach aims at improved long-term outcomes by adjusting therapy to resolve intestinal inflammation. The therapeutic options for UC are continually expanding. Risk-stratified therapy and the treat-to-target approach represent paradigm shifts in UC management. Optimal disease control requires an individualized approach that takes into consideration current inflammatory burden, long-term risk, patient preferences, and ongoing assessment of response to treatment.

Genome-Wide Association Study Identifies African-Specific Susceptibility Loci in African Americans With Inflammatory Bowel Disease.

BACKGROUND & AIMS: The inflammatory bowel diseases (IBD) ulcerative colitis (UC) and Crohn's disease (CD) cause significant morbidity and are increasing in prevalence among all populations, including African Americans. More than 200 susceptibility loci have been identified in populations of predominantly European ancestry, but few loci have been associated with IBD in other ethnicities. METHODS: We performed 2 high-density, genome-wide scans comprising 2345 cases of African Americans with IBD (1646 with CD, 583 with UC, and 116 inflammatory bowel disease unclassified) and 5002 individuals without IBD (controls, identified from the Health Retirement Study and Kaiser Permanente database). Single-nucleotide polymorphisms (SNPs) associated at P < 5.0 × 10-8 in meta-analysis with a nominal evidence (P < .05) in each scan were considered to have genome-wide significance. RESULTS: We detected SNPs at HLA-DRB1, and African-specific SNPs at ZNF649 and LSAMP, with associations of genome-wide significance for UC. We detected SNPs at USP25 with associations of genome-wide significance for IBD. No associations of genome-wide significance were detected for CD. In addition, 9 genes previously associated with IBD contained SNPs with significant evidence for replication (P < 1.6 × 10-6): ADCY3, CXCR6, HLA-DRB1 to HLA-DQA1 (genome-wide significance on conditioning), IL12B,PTGER4, and TNC for IBD; IL23R, PTGER4, and SNX20 (in strong linkage disequilibrium with NOD2) for CD; and KCNQ2 (near TNFRSF6B) for UC. Several of these genes, such as TNC (near TNFSF15), CXCR6, and genes associated with IBD at the HLA locus, contained SNPs with unique association patterns with African-specific alleles. CONCLUSIONS: We performed a genome-wide association study of African Americans with IBD and identified loci associated with UC in only this population; we also replicated IBD, CD, and UC loci identified in European populations. The detection of variants associated with IBD risk in only people of African descent demonstrates the importance of studying the genetics of IBD and other complex diseases in populations beyond those of European ancestry.

Update on the Use of Thiopurines and Methotrexate in Inflammatory Bowel Disease.

PURPOSE OF REVIEW: The increased use of biologic agents over the past two decades has led to a reappraisal of the role of the immunomodulators (thiopurines and methotrexate) in the treatment of inflammatory bowel disease. The purpose of this review is to summarize recent data on the use of thiopurines and methotrexate either as monotherapy or as part of combination therapy with biologic agents. RECENT FINDINGS: Recent studies have addressed the need for concomitant immunomodulatory therapy in treatment-naïve patients starting anti-TNF-α therapy, the appropriate dose of the immunomodulator in this setting, the minimum duration of combination therapy, and the possible mechanisms by which immunomodulators enhance the effectiveness of anti-TNF-α agents. Little is known about the role of immunomodulators in combination with agents belonging to other classes of biologic therapies. Recent studies have shown that methotrexate is not effective in inducing or maintaining remission in ulcerative colitis. Finally, several studies have broadened our understanding of the infection and malignancy risks of the immunomodulators. Immunomodulators continue to have a place in the treatment of inflammatory bowel disease. However, with the ever-increasing list of biologic agents, properly positioning the immunomodulators within the overall therapeutic scheme is a complicated task. In order to optimize outcomes, each patient requires an individualized approach, which takes into account risks, benefits, cost, alternatives, and patient preferences.

Knowledge Gaps in the Management of Postoperative Crohn's Disease: A US National Survey.

BACKGROUND: Postoperative recurrence (POR) of Crohn's disease (CD) is common. Guidelines on POR management have recently been issued, but clinical practice may vary. AIMS: To examine the current clinical practice of POR management in the USA METHODS: A web-based survey was sent to all members of the American Gastroenterological Association and the American College of Gastroenterology. The survey consisted of multiple-choice questions with clinical scenarios to assess how participants manage POR. RESULTS: A total of 189 responses were received from practices in 34 states. 44% of participants were from academic settings. The median number of CD patients seen each month was 20-30 patients per participant. The majority of participants considered smoking, prior intestinal surgery, penetrating disease, perianal fistula, early disease onset, and long extent of disease as high-risk factors for POR. To diagnose and grade endoscopic recurrence, 57% of participants used an endoscopic scoring system; 86% defined clinical recurrence using a combination of symptoms and endoscopic findings; and 79% of participants routinely performed colonoscopy after surgery. In high-risk patients, 65% offered medical prophylaxis-most often biologics and/or immunomodulators-immediately after surgery, while 34% offered medical prophylaxis regardless of the patient's risk of POR. 64% of participants never stopped medical prophylaxis once initiated. CONCLUSIONS: Most gastroenterologists routinely perform colonoscopy to guide POR management. The majority of these providers continue medical prophylaxis indefinitely regardless of subsequent endoscopic findings. Further research is needed to determine the risks and benefits of continuing versus deescalating therapy in patients with potentially surgically induced remission.

Characterization of genetic loci that affect susceptibility to inflammatory bowel diseases in African Americans.

BACKGROUND & AIMS: Inflammatory bowel disease (IBD) has familial aggregation in African Americans (AAs), but little is known about the molecular genetic susceptibility. Mapping studies using the Immunochip genotyping array expand the number of susceptibility loci for IBD in Caucasians to 163, but the contribution of the 163 loci and European admixture to IBD risk in AAs is unclear. We performed a genetic mapping study using the Immunochip to determine whether IBD susceptibility loci in Caucasians also affect risk in AAs and identify new associated loci. METHODS: We recruited AAs with IBD and without IBD (controls) from 34 IBD centers in the United States; additional controls were collected from 4 other Immunochip studies. Association and admixture loci were mapped for 1088 patients with Crohn's disease, 361 with ulcerative colitis, 62 with IBD type unknown, and 1797 controls; 130,241 autosomal single-nucleotide polymorphisms (SNPs) were analyzed. RESULTS: The strongest associations were observed between ulcerative colitis and HLA rs9271366 (P = 7.5 × 10(-6)), Crohn's disease and 5p13.1 rs4286721 (P = 3.5 × 10(-6)), and IBD and KAT2A rs730086 (P = 2.3 × 10(-6)). Additional suggestive associations (P < 4.2 × 10(-5)) were observed between Crohn's disease and IBD and African-specific SNPs in STAT5A and STAT3; between IBD and SNPs in IL23R, IL12B, and C2orf43; and between ulcerative colitis and SNPs near HDAC11 and near LINC00994. The latter 3 loci have not been previously associated with IBD, but require replication. Established Caucasian associations were replicated in AAs (P < 3.1 × 10(-4)) at NOD2, IL23R, 5p15.3, and IKZF3. Significant admixture (P < 3.9 × 10(-4)) was observed for 17q12-17q21.31 (IZKF3 through STAT3), 10q11.23-10q21.2, 15q22.2-15q23, and 16p12.2-16p12.1. Network analyses showed significant enrichment (false discovery rate <1 × 10(-5)) in genes that encode members of the JAK-STAT, cytokine, and chemokine signaling pathways, as well those involved in pathogenesis of measles. CONCLUSIONS: In a genetic analysis of 3308 AA IBD cases and controls, we found that many variants associated with IBD in Caucasians also showed association evidence with these diseases in AAs; we also found evidence for variants and loci not previously associated with IBD. The complex genetic factors that determine risk for or protection against IBD in different populations require further study.

Impact of retroflexion vs. second forward view examination of the right colon on adenoma detection: a comparison study.

OBJECTIVES: Although screening colonoscopy is effective in preventing distal colon cancers, effectiveness in preventing right-sided colon cancers is less clear. Previous studies have reported that retroflexion in the right colon improves adenoma detection. We aimed to determine whether a second withdrawal from the right colon in retroflexion vs. forward view alone leads to the detection of additional adenomas. METHODS: Patients undergoing screening or surveillance colonoscopy were invited to participate in a parallel, randomized, controlled trial at two centers. After cecal intubation, the colonoscope was withdrawn to the hepatic flexure, all visualized polyps removed, and endoscopist confidence recorded on a 5-point Likert scale. Patients were randomized to a second exam of the proximal colon in forward (FV) or retroflexion view (RV), and adenoma detection rates (ADRs) compared. Logistic regression analysis was used to evaluate predictors of identifying adenomas on the second withdrawal from the proximal colon. RESULTS: A total of 850 patients (mean age 59.1±8.3 years, 59% female) were randomly assigned to FV (N=400) or RV (N=450). Retroflexion was successful in 93.5%. The ADR (46% FV and 47% RV) and numbers of adenomas per patient (0.9±1.4 FV and 1.1±2.1 RV) were similar (P=0.75 for both). At least one additional adenoma was detected on second withdrawal in similar proportions (10.5% FV and 7.5% RV, P=0.13). Predictors of identifying adenomas on the second withdrawal included older age (odds ratio (OR)=1.04, 95% confidence interval (CI)=1.01-1.08), adenomas seen on initial withdrawal (OR=2.8, 95% CI=1.7-4.7), and low endoscopist confidence in quality of first examination of the right colon (OR=4.8, 95% CI=1.9-12.1). There were no adverse events. CONCLUSIONS: Retroflexion in the right colon can be safely achieved in the majority of patients undergoing colonoscopy for colorectal cancer screening. Reexamination of the right colon in either retroflexed or forward view yielded similar, incremental ADRs. A second exam of the right colon should be strongly considered in patients who have adenomas discovered in the right colon, particularly when endoscopist confidence in the quality of initial examination is low.

Tricyclic antidepressants for management of residual symptoms in inflammatory bowel disease.

BACKGROUND: Tricyclic antidepressants (TCAs) have efficacy in treating irritable bowel syndrome (IBS). Some clinicians use TCAs to treat residual symptoms in inflammatory bowel disease (IBD) patients already on decisive IBD therapy or with quiescent inflammation, although this strategy has not been formally studied. GOALS: The aim of this study was to examine the efficacy of TCA therapy in IBD patients with residual symptoms, despite controlled inflammation, in a retrospective cohort study. STUDY: Inclusion required initiation of TCA for persistent gastrointestinal symptoms. IBD patients had inactive or mildly active disease with persistent symptoms despite adequate IBD therapy as determined by their physician. Symptom response was compared with IBS patients. Established Likert scales were used to score baseline symptom severity (0=no symptoms, 3=severe symptoms) and TCA response (0=no improvement; 3=complete satisfaction). RESULTS: Eighty-one IBD [41.3±1.7 y, 56F; 58 Crohn's disease/23 ulcerative colitis (UC)] and 77 IBS (46.2±1.7 y, 60F) patients were initiated on a TCA therapy. Baseline symptom scores (IBD, 2.06±0.03; IBS, 2.12±0.04; P=0.15) and symptom response to TCA therapy (IBD, 1.46±0.09; IBS, 1.30±0.09; P=0.2) were similar in both the groups. At least moderate improvement (Likert score ≥2) on TCA was achieved by comparable proportions of patients (59.3% IBD vs. 46% IBS; P=0.09). Within IBD, response was better with UC than Crohn's disease (1.86±0.13 vs. 1.26±0.11, respectively, P=0.003). CONCLUSIONS: In a clinical practice setting, TCA use led to moderate improvement of residual gastrointestinal symptoms in IBD patients for whom escalation of IBD therapy was not planned. UC patients demonstrated higher therapeutic success. IBD symptom responses were similar to IBS patients.

Positioning therapy for Crohn's disease.

The therapy of Crohn's disease is constantly evolving. It is widely recognized that clinical assessment does not stage disease activity accurately and that endoscopic healing is associated with improved long-term outcomes. Disease management is therefore transitioning to a new paradigm that includes direct assessment of disease severity (endoscopically in most patients), followed by assessment of mucosal healing. New approaches have helped optimize the use of the thiopurines, methotrexate and anti-TNF agents. Novel agents with different mechanisms of action are expanding our therapeutic armamentarium. The major challenge of the future will be to identify patient subgroups best suited to particular therapeutic approaches. In the meantime, studies of comparative effectiveness will be crucial in positioning therapies relative to each other.

Comparative maintenance performance of all biologic agents and small molecules in ulcerative colitis: a network meta-analysis.

BACKGROUND AND AIMS: Βiologic agents and small molecules have expanded the therapeutic armamentarium of moderate to severe ulcerative colitis (UC). However, their comparative efficacy and safety performance as maintenance treatments have not been sufficiently explored. We performed a systematic review and network meta-analysis (NWM) to assess the comparative efficacy and safety of all approved and emerging treatments for maintenance in moderate to severe UC. METHODS: We searched Pubmed/Medline, EMBASE, and Cochrane Library databases for relevant RCTs through April 2023. The primary endpoint was clinical remission at the end of the maintenance therapy. Data were analyzed by means of a Bayesian NWM. The ranking probability concerning efficacy and safety was evaluated by means of surfaces under cumulative ranking (SUCRA) values. RESULTS: There were 20 eligible RCTs with 7660 patients randomized to 20 treatments. RCTs were grouped into two study designs, that is, re-randomization of patients after an induction period and treat-through patients. Concerning efficacy, in re-randomized patients, upadacitinib 30 mg/day was ranked first (SUCRA 94.9%) whereas in treat-through patients etrasimod 2 mg/day was ranked first (SUCRA 91.1%). The integrated efficacy-safety hierarchical analysis, showed that tofacitinib 10 mg had the best efficacy-safety therapeutic profile in re-randomized patients, whereas in treat-through patients infliximab 3.5 mg/Kg Q8W showed the best efficacy-safety profile. CONCLUSION: For maintenance treatment, in moderate to severe UC, this NWM showed that upadacitinib 30 mg/day and etrasimod 2 mg/day were ranked best for efficacy in re-randomized and treat-through patients respectively. Tofacitinib 10 mg/day and infliximab 3.5 mg/Kg Q8W showed the best efficacy-safety therapeutic profile in re-randomized and treat-through patients respectively.

Inner mitochondrial membrane protein Prohibitin 1 mediates Nix-induced, Parkin-independent mitophagy.

Autophagy of damaged mitochondria, called mitophagy, is an important organelle quality control process involved in the pathogenesis of inflammation, cancer, aging, and age-associated diseases. Many of these disorders are associated with altered expression of the inner mitochondrial membrane (IMM) protein Prohibitin 1. The mechanisms whereby dysfunction occurring internally at the IMM and matrix activate events at the outer mitochondrial membrane (OMM) to induce mitophagy are not fully elucidated. Using the gastrointestinal epithelium as a model system highly susceptible to autophagy inhibition, we reveal a specific role of Prohibitin-induced mitophagy in maintaining intestinal homeostasis. We demonstrate that Prohibitin 1 induces mitophagy in response to increased mitochondrial reactive oxygen species (ROS) through binding to mitophagy receptor Nix/Bnip3L and independently of Parkin. Prohibitin 1 is required for ROS-induced Nix localization to mitochondria and maintaining homeostasis of epithelial cells highly susceptible to mitochondrial dysfunction.

A decision fusion strategy for polyp detection in capsule endoscopy.

Wireless capsule endoscopy (CE) is now routinely used for non-invasive diagnosis of small bowel diseases. But, it still requires manual assessment of the approximately 50,000 study images. Literature has recently investigated automated methods to detect and analyze various anomalies in CE images to improve reading efficiency and reduce variability. We propose such a computer aided diagnosis (CAD) approach to detect small bowel polyps. For supervised classification of polyps, we investigated fusing multiple statistical classifiers based on color, texture and edge features. The combined boosted classifier when evaluated using 1200 CE images outperformed all individual classifiers and achieved a ~90% classification accuracy.

Treatment persistence and maintenance dose titration among ulcerative colitis patients on biologics: a pooled study of three United States claim databases.

OBJECTIVE: This real-world study evaluated biologic treatment patterns in patients with moderate-to-severe ulcerative colitis (UC). METHODS: IQVIA PharMetrics, IBM MarketScan, and Optum Clinformatics were pooled to identify UC patients with ≥1 claim for UC and ≥1 claim for adalimumab (ADA), golimumab (GOL), infliximab (IFX), or vedolizumab (VDZ). The index date for each biologic was the first claim for that biologic. Patients could be included in >1 cohort if they switched biologics during the identification period. Continuous eligibility for medical/pharmacy benefits was required for 12 months before (baseline) and after (follow-up) the index date. Patients lacking claims for any biologic during baseline were categorized as bio-naïve; those with any biologic claim were categorized as bio-experienced. Persistence was defined as the proportion of patients that remained on the index biologic without a gap between claims of >28 days for ADA, >56 days for GOL, and >112 days for IFX and VDZ. Dose titration was assessed among patients with ≥2 maintenance doses during follow-up among ADA, GOL, and VDZ patients. RESULTS: In total, 6,106 bio-naïve UC patients and 1,027 bio-experienced UC patients were identified. Patients treated with VDZ and IFX had the highest persistence followed by ADA and GOL patients for bio-naïve and bio-experienced, respectively. ADA patients had a numerically higher proportion of patients with 50% dose escalation, followed by VDZ and GOL; 50% dose reduction was observed in ≤1% patients. CONCLUSIONS: In this descriptive study of UC patients without confounder adjustment, VDZ persistence was numerically highest followed by IFX, GOL, and ADA across both populations.

The Development and Initial Findings of A Study of a Prospective Adult Research Cohort with Inflammatory Bowel Disease (SPARC IBD).

BACKGROUND: Clinical and molecular subcategories of inflammatory bowel disease (IBD) are needed to discover mechanisms of disease and predictors of response and disease relapse. We aimed to develop a study of a prospective adult research cohort with IBD (SPARC IBD) including longitudinal clinical and patient-reported data and biosamples. METHODS: We established a cohort of adults with IBD from a geographically diverse sample of patients across the United States with standardized data and biosample collection methods and sample processing techniques. At enrollment and at time of lower endoscopy, patient-reported outcomes (PRO), clinical data, and endoscopy scoring indices are captured. Patient-reported outcomes are collected quarterly. The quality of clinical data entry after the first year of the study was assessed. RESULTS: Through January 2020, 3029 patients were enrolled in SPARC, of whom 66.1% have Crohn's disease (CD), 32.2% have ulcerative colitis (UC), and 1.7% have IBD-unclassified. Among patients enrolled, 990 underwent colonoscopy. Remission rates were 63.9% in the CD group and 80.6% in the UC group. In the quality study of the cohort, there was 96% agreement on year of diagnosis and 97% agreement on IBD subtype. There was 91% overall agreement describing UC extent as left-sided vs extensive or pancolitis. The overall agreement for CD behavior was 83%. CONCLUSION: The SPARC IBD is an ongoing large prospective cohort with longitudinal standardized collection of clinical data, biosamples, and PROs representing a unique resource aimed to drive discovery of clinical and molecular markers that will meet the needs of precision medicine in IBD.

Targeting Mitochondrial Damage as a Therapeutic for Ileal Crohn's Disease.

Paneth cell defects in Crohn's disease (CD) patients (called the Type I phenotype) are associated with worse clinical outcomes. Recent studies have implicated mitochondrial dysfunction in Paneth cells as a mediator of ileitis in mice. We hypothesized that CD Paneth cells exhibit impaired mitochondrial health and that mitochondrial-targeted therapeutics may provide a novel strategy for ileal CD. Terminal ileal mucosal biopsies from adult CD and non-IBD patients were characterized for Paneth cell phenotyping and mitochondrial damage. To demonstrate the response of mitochondrial-targeted therapeutics in CD, biopsies were treated with vehicle or Mito-Tempo, a mitochondrial-targeted antioxidant, and RNA transcriptome was analyzed. During active CD inflammation, the epithelium exhibited mitochondrial damage evident in Paneth cells, goblet cells, and enterocytes. Independent of inflammation, Paneth cells in Type I CD patients exhibited mitochondrial damage. Mito-Tempo normalized the expression of interleukin (IL)-17/IL-23, lipid metabolism, and apoptotic gene signatures in CD patients to non-IBD levels. When stratified by Paneth cell phenotype, the global tissue response to Mito-Tempo in Type I patients was associated with innate immune, lipid metabolism, and G protein-coupled receptor (GPCR) gene signatures. Targeting impaired mitochondria as an underlying contributor to inflammation provides a novel treatment approach for CD.

Rheostat regulation of integrin-mediated leukocyte adhesion.

The homing of activated T lymphocytes to the gut in inflammatory bowel diseases is dependent on their coordinated, integrin-mediated adhesion and de-adhesion to substrates and blood vessel walls. In this issue of the JCI, Park and colleagues reveal a key modulatory role of a binding site within beta integrins, known as the ADMIDAS domain, in controlling integrin de-adhesion in mice (see the related article beginning on page 2526). These observations add to our growing understanding of how integrin adhesiveness is regulated and raise the notion of the existence of a biological rheostat for lymphocyte homing. Disturbed migratory rheostat tone could account for variations in interindividual immune responses observed in patients with inflammatory bowel disease or other lymphocyte-mediated inflammatory disorders. These findings will inform future strategies to design small molecules for the treatment of a spectrum of chronic inflammatory conditions.

NOD2 mutations and anti-Saccharomyces cerevisiae antibodies are risk factors for Crohn's disease in African Americans.

OBJECTIVES: NOD2 mutations and anti-Saccharomyces cerevisiae antibodies (ASCAs) are established risk factors of Crohn's disease (CD) in whites but have not been assessed in African-American (AA) adults with CD. METHODS: AAs with CD and controls were recruited by the Mid-Atlantic African-American IBD Study as part of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) IBD Genetics Consortium. Genotyping for the three common CD NOD2 mutations (Leu1007fsinsC, G908R/2722g>c, and R702W/2104c>t) and ASCA enzyme-linked immunosorbent assays were performed in 183 AA CD patients and in 143 controls. Logistic regression was used to calculate adjusted odds ratios (ORs) for the association between ASCA and disease phenotype. RESULTS: ASCA sensitivity and specificity values were 70.5 and 70.4%, respectively. On univariate analysis, ASCA was significantly associated with younger age at diagnosis, ileal involvement, and complicated (stricturing/penetrating) behavior. On multivariate analysis, ASCA titer (per 25 Units) was associated with ileal involvement (OR 1.18, 95% confidence interval (CI): 1.04-1.34), complicated behavior (OR 1.13, 95% CI: 1.01-1.28), and surgery (hazard ratio: 1.11, 95% CI: 1.02-1.21). Cigarette smoking and CD family history were also significantly associated with surgery. NOD2 carriers (all heterozygotes) were more common among CD cases than controls (8.2 vs. 2.1%; OR 4.17%, 95% CI: 1.18-14.69). The NOD2 mutation population attributable risk was 6.2%. CONCLUSIONS: In comparison with whites, ASCA in AAs has a similar sensitivity but a lower specificity for CD. ASCA is associated with ileal involvement, complicated behavior, and surgery in AAs with CD. NOD2 is a risk gene for AA CD, although mutation frequency and population attributable risk are much lower than in whites.