Tag Archives: gut microbiome

Elegant Study: Childhood Exposure to a Sibling with Crohn’s Disease and Disease Susceptibility

Posted on by
Reply

R Chen et al. Gut. Epub ahead of print, August 31, 2026. doi:10.1136/
gutjnl-2026-339257. Childhood exposure to a sibling with Crohn’s disease alters gut microbiome and Crohn’s disease susceptibility

Thanks to Mike Hart for sharing this reference. This study is worth reading in its entirety due to the combination of experiments. This is a fairly long post to summarize the most important findings.

Background:

“In a study of 2756 Dutch families, gut microbiome composition and function were more alike between siblings than between parent-offspring pairs or spouses…These findings suggest that increased disease susceptibility among siblings of individuals with CD may be mediated by their shared gut microbiome.”

Methods:

  1. The authors used the prospective Genetic Environmental Microbial (GEM) Project and the nationwide South Korean database to assess the association between childhood exposure to affected siblings and CD onset (n=3126). This was validated in the South Korean dataset.
  2. A T-cell transfer model of colitis in germ-free mice was conducted to investigate the effects of stool from childhood-exposed (n=4) versus adult-exposed (n=4) siblings.
  3. An integrative risk model combining faecal calprotectin (FCP) and microbial enterotypes was trained and internally validated within the GEM cohort.

Key findings:

  • “In the GEM cohort, childhood exposure to an affected sibling was associated with a fourfold higher risk of developing CD compared with adult exposure (adjusted HR (aHR) 4.00; p=5.3×10−4), which was validated in the South Korean dataset (aHR 2.54; p=6.0×10−6).”
  • “Childhood exposure was associated with reduced abundances of Lachnospira,
    Roseburia     and Colidextribacter, reductions that mediation analysis identified as partially mediating CD risk.”
  • “In vivo, transplantation of childhood exposure-associated microbiota into germ-free recipient mice exacerbated colitis and elevated mucosal interleukin-22 expression, supporting a potential mechanistic role.”
  • This “model identified siblings with elevated FCP and Blautia-enriched or
    Prevotella-enriched enterotypes as highest risk, with a 10-year cumulative incidence of 22.5%.”
Figure 1b. Childhood exposure to CD was demonstrated to associate with increased disease susceptibility in the GEM cohort, and confirmed in an independent nationwide dataset.
Figure 1d. Among siblings with childhood exposure to CD, the authors developed and validated a risk stratification based on gut inflammation and enterotypes to identify individuals at high risk of CD onset
Figure 3a. Bar chart presenting the proportion of individuals with gut barrier dysfunction and gut inflammation among those exposed to CD during childhood (blue) or adulthood (orange).
Figure 5d. Kaplan-Meier curves showing the cumulative CD-free probability for individuals classified as having non-inflammation (blue), gut inflammation with Bact2 (green) and gut inflammation with Blau/Prev (orange) in the GEM cohort.

Discussion

  • This “study demonstrates that the timing of exposure to a sibling with CD, specifically childhood versus adult exposure, plays a critical role in disease susceptibility. Childhood exposure was associated with a fourfold higher risk of CD, potentially mediated by alterations in the gut microbiome.”
  • “Genetic predisposition has traditionally been considered the primary explanation for the elevated disease risk among siblings of persons with CD. However, genetic factors account for only about 10% of the variance in CD risk…childhood exposure to a sibling
    with CD, compared with adulthood exposure, was associated with a fourfold increased risk of disease onset, independent of the CD-PRS [CD – polygenic risk score].”
  • This study adds to “a growing body of evidence [that] implicates early-life exposures in CD pathogenesis. A recent meta-analysis reported that prenatal exposure to antibiotics and cigarette smoking increased the risk of CD, while breastfeeding was protective. Similarly, a large population-based study found that rural residence during childhood, but not adulthood, was associated with a lower risk of CD.”

Limitations:

  • Participants were from high-income countries.
  • Study did not include dietary intake.
  • These findings do not prove causation. There may be additional unrecognized genetic factors between the groups with exposure before and after 18 years of age.

My take: The increasing prevalence of Crohn’s disease, particularly over the last few decades, must be related to environmental factors; population genetics and genetic predisposition are unlikely to rapidly change. This is a very important study supporting the notion that exposure to siblings with Crohn’s disease and alteration of the gut microbiome increases the risk of Crohn’s disease. By identifying a microbiome group with a higher risk, this study may facilitate research to determine whether manipulation of the gut microbiome could reduce the likelihood of developing Crohn’s disease. If we can reduce Crohn’s disease in a high risk population, it may allow broader use of the same treatment principles to lower risk groups as well.

Related blog posts:

Genetically-Modified Gut Bacteria

Posted on by

A recent NPR story (A Gulp Of Genetically Modified Bacteria Might Someday Treat A Range Of Illnesses) explored new research regarding ingestion of genetically modified gut bacteria for medical purposes.

Two of the examples that were highlighted included phenylketonuria (PKU) and cirrhosis.  For each disorder, the researchers are modifying E coli. For PKU, this may allow individuals to consume foods like milk and meat that usually would make them sick because individuals with PKU develop toxicity in response to phenylalanine in their diet.  For cirrhosis, the genetically modified E coli help eliminate the elevation of ammonia which is due in part to gut bacteria and in part due to liver dysfunction.  The report notes that the application of this science is likely to impact many other disorders including ulcerative colitis.

These efforts represent an exponential change to modifying the gut microbiome to enhance health.

Related blog posts: