Tuesday, 8 November 2016

"A Putative Blood-Based Biomarker for Autism Spectrum Disorder-Associated Ileocolitis"

Contrary to Murphy's Law - 'never repeat a successful experiment' - replication or reproducibility is a cornerstone of good science. Today, I'm blogging about a piece of research that aimed to do just that as per the findings reported by Stephen Walker and colleagues [1] (open-access).

The title of this post has been borrowed from the title of the Walker paper to illustrate how moving on from the quite widely known 'fact' that functional gastrointestinal (GI) symptoms are over-represented when it comes to the label of autism (see here for example) so further research focus is required on more pathological bowel conditions potentially linked to autism too (see here). Yes, I know this potentially takes us into some uncomfortable territory but for those with autism suffering with various bowel issues (and I do mean suffering) this marks some important science for them and their families onward to the resolution of any further health inequalities.

The latest Walker paper follows on from their original findings [2] which have been previously covered on this blog (see here) observing that: "ASDGI children have a gastrointestinal mucosal molecular profile that overlaps significantly with known inflammatory bowel disease (IBD), yet has distinctive features that further supports the presence of an ASD-associated IBD variant, or, alternatively, a prodromal phase of typical inflammatory bowel disease." ASDGI by the way, referred to their small grouping of "twenty five consecutive ASDGI cases (6 autism; 19 autism spectrum disorder) with histopathologic findings of ileitis, colitis, or both."

This latest time around authors report on the extending of their 'initial findings' in "an additional case/control cohort." Further they "report a gene expression profile in peripheral blood that may reflect the presence of ASD-associated ileocolitis and provide a putative surrogate biomarker that, upon validation, would be of significant clinical relevance." Potentially, big words.

The paper is open-access but here are a few choice details:

  • Biopsy samples - "a specimen from each of seven anatomic locations (from the terminal ileum to rectum)" - and blood samples were provided by 21 participants (patients) diagnosed with an autism spectrum disorder (ASD). All presented with gastrointestinal (GI) symptoms and all had "a history of normal development for at least 12 months followed by developmental regression and onset of gastrointestinal symptoms." All also had "histologically-confirmed ileitis, colitis, or both in at least one of seven collected and archived colonic biopsies.
  • A control group of 21 'typically-developing' children "without ASD who had gastrointestinal symptoms... but no identifiable histologic inflammation on any biopsies in either the ileum or colon" were also included for analysis.
  • Part 1 of the study "compared whole genome gene expression profiles of inflamed ASD GI mucosal tissue (ASDIC+) to non-inflamed TD mucosal tissue (TDIC−) in biopsies from both the terminal ileum and colon." This is pretty much what was done by the authors during their first research voyage in this area. Part 2 was more novel insofar as blood gene expression profiles were compared between the groups. It's also important to note that: "blood was obtained from the same patients, and at the same time, as their respective mucosal tissue samples."
  • Results: applying a statistical technique called Principal Component Analysis (PCA) looking at gene expression in those mucosal (bowel) samples, authors were again able to say that there were differences between inflamed and non-inflamed samples/groups. They also observed some potentially important differences in those blood samples too: "Nine of these DETs [gene transcripts that are differentially-expressed] were also differentially expressed in blood in our most recent cohort." You might ask what does this actually tell us about the autism+GI group? Well, nothing and something, insofar as it is not really being ethical to start taking bowel biopsies from children with autism without any indication to do so, which means that comparisons between non-GI and GI+ children with autism were not possible. The data do however suggest that a "putative peripheral marker could provide a proxy for gastrointestinal inflammation and also provide functional insights."
  • Insofar as the details of what genes were being differentially expressed in ASDIC+ vs. TDIC- samples and how these overlapped with the previous study from the authors, there were some interesting candidates including "a key mitochondrial folate pathway gene, MTHFD2 (methylenetetrahydrofolate dehydrogenase (NADP + dependent) 2, methenyltetrahydrofolate cyclohydrolase)" hinting at an effect beyond just immune function and inflammation/inflammatory signalling. Authors modelled various combinations of these genes expressed (or not) to try and come up with some preliminary Receiver Operating Characteristic (ROC) curve analysis. Regular readers of this blog will probably have heard me talk about ROC analyses before (see here for example) with regards to the search for potential classifiers or biomarker profiles associated with autism. Bearing in mind the small participant numbers included in this study and the final figures arrived at, I'd suggest that quite a bit more work is required before anyone takes the reported findings as gospel just yet. But they are interesting...

So, there you have it. This is important work for two reasons: (i) more pathological bowel states can and do present alongside autism [3] (the diagnosis of autism is seemingly protective of very little as science is learning) and (ii) with the strong requirement for further investigations in this area, science is seemingly starting on a path to potentially identifying blood-based 'biomarkers' possibly useful in identifying those who might benefit from further screening for such bowel issues.

Given the history and debate in the area of bowel disease accompanying some autism, I'm not expecting giant fanfares to greet these results nor any big rush to try and prove/disprove these latest findings. That is an unfortunate truth and in the end, it is the children/adults with autism and significant GI issues who lose out as a consequence. The fact that this and the previous work by the authors is peer-reviewed science and not just speculation however will I think eventually be important, as talk about medical comorbidity accompanying autism continues at a pace [4] (see here too) and further moves towards 'what can we do about such issues?' eventually start to come to the forefront.

And just before I go, there may also be other research uses for biopsies as and when they have to be taken from children/adults under clinical investigation [5]...

To close, I note there is an election across the Pond. With all the nastiness that has followed the campaign, surely there's an easier way to pick the Leader of the Free World...

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[1] Walker SJ. et al. A Putative Blood-Based Biomarker for Autism Spectrum Disorder-Associated Ileocolitis. Sci Rep. 2016 Oct 21;6:35820.

[2] Walker SJ. et al. Identification of unique gene expression profile in children with regressive autism spectrum disorder (ASD) and ileocolitis. PLoS One. 2013;8(3):e58058.

[3] Doshi-Velez F. et al. Prevalence of Inflammatory Bowel Disease Among Patients with Autism Spectrum Disorders. Inflamm Bowel Dis. 2015 Oct;21(10):2281-8.

[4] Vohra R. et al. Comorbidity prevalence, healthcare utilization, and expenditures of Medicaid enrolled adults with autism spectrum disorders. Autism. 2016. Oct 20.

[5] Kushak RI. et al. Analysis of the Duodenal Microbiome in Autistic Individuals: Association with Carbohydrate Digestion. J Pediatr Gastroenterol Nutr. 2016 Nov 2.

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ResearchBlogging.org Walker SJ, Beavers DP, Fortunato J, & Krigsman A (2016). A Putative Blood-Based Biomarker for Autism Spectrum Disorder-Associated Ileocolitis. Scientific reports, 6 PMID: 27767057