To Örebro University

BACKGROUND AND AIMS: Biomarkers are needed to identify individuals at elevated risk of inflammatory bowel disease (IBD). This study aims to identify protein signatures predictive of IBD.

METHODS: Using large population-based cohorts (n≥180,000), blood samples were obtained from individuals who later in life were diagnosed with IBD and compared to age and sex-matched controls, free from IBD during follow-up. 178 proteins were measured on Olink platforms. We used machine learning methods to identify protein signatures of preclinical disease in the discovery cohort (n=312). Their performance was validated in an external preclinical cohort (n=222) and assessed in an inception cohort (n=144) and a preclinical twin cohort (n=102).

RESULTS: In the discovery cohort, a signature of 29 proteins differentiated preclinical Crohn's disease (CD) cases from controls, with an area under the curve (AUC) of 0.85. Its performance was confirmed in the preclinical validation (AUC=0.87) and the inception cohort (AUC=1.0). In preclinical samples, downregulated (but not upregulated) proteins related to gut barrier integrity and macrophage functionality correlated with time to diagnosis of CD. The preclinical ulcerative colitis (UC) signature had a significant, albeit lower, predictive ability in the discovery (AUC=0.77), validation (AUC=0.67), and inception cohorts (AUC=0.95). The preclinical signature for CD demonstrated an AUC of 0.89 when comparing twins with preclinical CD to matched external healthy twins, but its predictive ability was lower (AUC=0.58; P=.04) when comparing them with their healthy twin siblings, i.e., when accounting for genetic and shared environmental factors.

CONCLUSION: We identified protein signatures for predicting a future diagnosis of CD and UC, validated across independent cohorts. In the context of CD, the signature offers potential for early prediction.

Objectives: Crohn's disease is characterized by a gut dysbiosis with decreased abundance of butyrate producers such as Faecalibacterium prausnitzii. Although F. prausnitzii secretes anti-inflammatory molecules, few studies have addressed the importance of F. prausnitzii in a longitudinal setting. We aimed to examine the relationship between temporal profiles of F. prausnitzii, the C. leptum group, overall butyrate production, and inflammatory activity.

Material and methods: Fecal samples (n = 59) were collected every third month from nine patients with ileal Crohn's disease. The abundance of F. prausnitzii and C. leptum was quantified relative to the total amount of bacteria using quantitative-PCR. To assess butyrate production of gut microbiota, gene copy numbers of the butyryl-CoA:acetate-CoA transferase (BCoAT) gene were quantified by qPCR. The inflammatory activity was defined by fecal (f)-calprotectin.

Results: No correlation between the relative abundance of F. prausnitzii, the C. leptum group, or copy numbers of the BCoAT gene, and f-calprotectin was observed in the total sample set. By analyzing alterations between consecutive samples, a negative correlation between changes in the relative abundance of F. prausnitzii and f-calprotectin was observed (R = -0.39; p = .009). Changes in C. leptum (R = -0.18, p = .23) and number of copies of the BCoAT gene (R = -0.12; p = .42) did not correlate with f-calprotectin.

Conclusions: There was an inverse correlation between temporal changes in the relative abundance of F. prausnitzii, but not overall butyrate producing capacity, and changes in inflammatory activity in ileal Crohn's disease. These findings indicate that F. prausnitzii may play a role in gut homeostasis, even though causality is still to be demonstrated.