A test "that distinguishes ASD fast response constipation from ASD persistent right-sided constipation"?

The quote heading this post - "A test that distinguishes ASD [autism spectrum disorder] fast response constipation from ASD persistent right-sided constipation" - comes from the findings reported by Stephen Walker and colleagues [1]. The Walker results continue a theme from this research group (see here) whereby some important data is being generated on how to treat some fairly prevalent bowel issues that seem to accompany quite a few diagnoses of autism (see here).

Much like other research from this authorship group, the research material examined was biopsy tissue - "ascending colon biopsy tissues" - provided by 35 children diagnosed with an autism spectrum disorder "and chronic constipation on a background of enterocolitis." I know some people don't like the word 'enterocolitis' in the context of autism (see here) but prejudices aside, there is nothing in the current research literature to suggest that a diagnosis of autism is somehow protective against the development of inflammatory bowel disease and/or its symptoms. Nothing.

Anyhow, 20 of those 35 children were categorised as 'slow responders' on the basis of showing "recurrent right-sided fecal loading requiring regular colon cleanouts during treatment for enterocolitis" and 15 were defined as 'fast responders' as a function of experiencing "a sustained state of GI [gastrointestinal] symptomatic remission while on maintenance anti-inflammatory therapy." In effect the group was divided up into those whose bowel symptoms got better (n=15) and those whose bowel symptoms did not (even after multiple attempts) (n=20). Researchers analysed those biopsy samples with the expression of genes in mind as per other research occasions [2].

Results: "Significant differences were found between the two clusters with fast responder-predominant cluster showing an upregulation of transcripts involved in the activation of immune and inflammatory response and the slow responder-predominant cluster showing significant over-representation of pathways impacting colonic motility (e.g. genes involved in tryptophan and serotonin degradation and mitochondrial dysfunction)." Apologies for the long quote taken from the Walker paper, but they said it better than I ever could. The translation: gene expression data was different between the fast and slow responder groups.

Obviously more research is needed in this area with larger participant groups and perhaps using samples from other non-autism groups who present (or don't) with various types of bowel issues, whether sensitive to treatment or not. The cluster of genes that were used in the authors' modelling did all right when it came to talk of possible 'biomakers' - "The sensitivity (sensitivity = 0.88), specificity (specificity = 0.89), and kappa (kappa = 0.77) statistics all reflect a good strength of agreement between prediction and actual assignments" - but still need more work before any big claims are made.

There are a couple of other things to mention from the Walker results. So, results suggested that: "predominantly chronic constipation in fast responders is not only related to the inflammatory status of the right colon but is likely a direct consequence of this colonic inflammation." Inflammation perhaps equalling constipation? Interesting. And it not only offers lots more avenues for further study but also some important treatment options.

Next, the amino acid tryptophan was singled out as being potentially "especially significant." I've always been interested in the aromatic amino acids in relation to some autism (see here). Tryptophan is a particularly important aromatic amino acid because it's eventually metabolised into a whole slew of important compounds from serotonin (5-HT) to melatonin and beyond, with some interesting connections to autism (see here). Walker and colleagues mention how: "In the slow responder cluster of patients, there was a significant upregulation of transcripts in each of the metabolic degradation pathways for tryptophan, serotonin, and melatonin, suggesting that TRP [tryptophan] insufficiency (and therefore 5-HT insufficiency) may be an important factor in the sustained hypomotility seen in this patient cohort." There's some much more study that one could do in this area. Particularly when 'gut hypomotility' is a potential issue for quite a few people on the autism spectrum (see here).

There are other things to consider from the Walker paper - "A third relevant theme apparent from the slow response gene expression profile involves a number of pathways that converge in the mitochondria and impact mitochondrial function" - but I'll leave that for now (see here). Suffice to say that there is enough evidence emerging in the peer-reviewed domain to say that (a) pathological bowel problems are more than present alongside a diagnosis of autism, (b) said bowel issues also overlap with functional GI symptoms such as constipation in particular, (c) there are physiological reasons for such bowel issues outside of any psychobabble explanations, and (d) lots more research is required in this area without fear or favour pertinent to improving quality of life...

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[1] Walker SJ. et al. A molecular biomarker for prediction of clinical outcome in children with ASD, constipation, and intestinal inflammation. Sci Rep. 2019 Apr 12;9(1):5987.

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

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Autism: a spectrum, dimensions or clusters? How about a multi-dimensional cluster of spectrums?

A write-up (see here) of the paper by Hyunsik Kim and colleagues [1] was the initial impetus for formulating this blog post, but it quickly escalated into something a little larger when the findings from Frank Duffy & Heidelise Als [2] also popped up.

The question at hand: how should one conceptualise autism? Is it truly a spectrum as per the Lorna Wing proposition, or is it something a trifle more complicated? As per the title of this post, should we perhaps be thinking about autism as some sort of "multi-dimensional cluster of spectrums?" I'll come back to that idea shortly.

Well, it's not for me to make definitive conclusions on this blog. Science rarely, if at all, provides an absolute 'truth' but rather the probability that something is approaching truth. Such a notion goes double when you consider the singular label of autism and the huge heterogeneity that it encompasses. There are no easy answers and probably little or no truths.

Starting with the Kim paper (including some notable names such as the surname 'Gadow') and the name of the research game was modelling, modelling in a computational sense. So: "The sample comprised 3,825 youth, who were consecutive referrals to a university developmental disabilities or child psychiatric outpatient clinic." The CASI-4R - formulated by Prof. Gadow - was the schedule administered, which includes "an ASD [autism spectrum disorder] symptom rating scale" among other things. Some nifty statistics were applied to the data and the initial findings were 'tested' on a further group of over 2500 children.

Results: "Based on comparison of 44 different models, results indicated that the ASD symptom phenotype is best conceptualized as multi-dimensional versus a categorical or categorical-dimensional hybrid construct." And the dimensions mentioned in that 'multi-dimensional' statement? Well, lucky for us they were something familiar: "social interaction, communication, and repetitive behaving."

Then to the Duffy/Als paper (again, these authors are no stranger to autism research) and a similar starting point: "The authors postulate that the broad definition of an omnibus 'spectrum disorder' may inhibit delineation of meaningful clinical correlations." Indeed, very familiar (see here). The conclusion: "evidence that an objectively defined, EEG [electroencephalogram] based brain measure may be helpful in illuminating the autism spectrum versus subgroups (clusters) question." The tool used by Duffy/Als in their study was something called NbClust "specifically designed to provide an objective means, i.e. independent of investigator choice, to identify the ‘optimal’ cluster number within a population." Said tool was applied to EEG data derived from 400 participants diagnosed with an ASD. Statistics and more statistics applied to the data revealed that: "430 subjects diagnosed as being on the autism “spectrum” and represented by 40 EEG coherence factors..., fell into two distinct clusters." These autism spectrum clusters differed from each other and importantly, from "554 subject neuro-typical control group subjects, not involved in the clustering process." Interesting results but an unfortunate use of the term 'neurotypical' (see here). Duffy & Als conclude that their data support a view whereby "autism disorder should not be seen as a continuous spectrum." So Kim & Duffy/Als arrive at similar conclusions: a singular 'spectrum' idea of autism is probably not the best way of conceptualising the essence of the label.

I would perhaps add in a little more evidence for the idea that 'multi-dimensional clusters of spectrums' is a potentially better fit. I used the words 'spectrums' (plural) because there is a growing body of evidence to support the idea of more than one 'type' of autism. I say that from the perspective of evidence for autism being 'acquired' under several different circumstances (e.g. accompanying inborn errors of metabolism, linked to exposure to certain infections or diseases, etc). There's also evidence that clinical profiles under the umbrella term autism are not uniform (e.g. regressive autism, the so-called 'optimal outcomers', differing developmental trajectories, etc). And when one looks at something like the success (or not) of intervention, it's plain to see that there is no universally shared genetics and/or biology of autism in the singular either (see here and see here for examples). Add in the idea that autism rarely appears in a diagnostic vacuum (see here) and that said comorbidity might 'cluster' in some subgroups of autism (see here), and I hope you can see why 'plural' might be a good addition to any attempt to re-conceptualise autism: spectrum, dimension, tapestry, cluster or however you think it should be defined...

Oh, and since we're on the topic of trying to conceptualise autism, a new book out recently has been reviewed in Nature (see here). It talks about how "conclusive findings about sex-linked brain differences have failed to materialize" which is particularly apt in relation to previous talk about 'extreme male brains' as a way of conceptualising [some] autism (see here). One quote I particularly liked from the review is this one: "The brain is no more gendered than the liver or kidneys or heart."

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[1] Kim H. et al. Quantifying the Optimal Structure of the Autism Phenotype: A Comprehensive Comparison of Dimensional, Categorical, and Hybrid Models. J Am Acad Child Adolesc Psychiatry. 2018 Oct 29. pii: S0890-8567(18)31894-X.

[2] Duffy FH. & Als H. Autism, spectrum or clusters? An EEG coherence study. BMC Neurol. 2019 Feb 14;19(1):27.

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Get your (autism genetics) kicks on root 66?

With the ever-increasing volumes of research being published in the peer-reviewed domain these days, one sometimes has to be a little creative to ensure that your research paper stands out and is not lost in the scientific noise. Quite a good way of getting noticed is to make sure that your paper catches the attention of your reader base. Y'know, give it a snappy title; something that social media might pick up on...

So it was that my attention was taken when coming across the paper by Diaz-Beltran and colleagues [1] (open-access) titled: 'A common molecular signature in ASD gene expression: following Root 66 to autism'. Root 66 and Route 66 eh?

The 'root 66' appearing in the title of the Diaz-Beltran paper actually refers to the results of an "integrated systems biology analysis of 9 independent gene expression experiments covering 657 autism, 9 mental retardation and developmental delay and 566 control samples to determine if a common signature exists and to test whether regulatory patterns in the brain relevant to autism can also be detected in blood." I might add that those are the authors words and not my own.

Including a familiar name on the authorship list - one Dennis Wall, he of 'boiling down ADOS' and 'screening triage by YouTube' fame - researchers used various automated statistical methods to see whether "a signature of autism can be found in the blood that might be a molecular echo of autism-related regulatory impairment in the brain." The identified signature included a collection of 66 genes based on their examination of "27 case–control biosets of 9 independent experiments" - the root 66 cluster.

That root 66 cluster was subsequently tested to see what genes might be connected and some data about "related biological functions" across various conditions including autism. I really can't provide anything more detailed about the hows and whys of this process as I am fast approaching the limits of my knowledge in this area. Suffice to say that there was some previous work on some of the root 66 genes with autism in mind (4 genes) and quite a few others "have been shown to interact directly with known autism candidates or have been implicated in other autism-related neurological disorders."

When it came to looking at what those root 66 genes might be doing (functionally), the authors reported that quite a few of the genes were involved in one of three processes: (1) brain growth and development with a side-order of "neuroendocrine activity", (2) nervous system inflammation and loss of neurological functions, and (3) neurodegeneration "and damage of the nervous system." In that last category the authors made an important point that genes thought to be connected with cases of autism are generally not 'autism-specific' in terms of their possible connections with other conditions and labels. Without scaremongering or wishing to equate autism with cancer, some of the root 66 genes have been mentioned with various cancers in mind; something that might be important for at least some people on the autism spectrum (see here). On the basis of their collected studies, they concluded that: "the Root 66 cluster is non-random and likely plays a role unique to autism."

It is important to understand that whilst this is an important piece of research, further independent validation of the root 66 cluster is required before anyone gets ahead of themselves. As per other examples where genetic 'markers' have been talked about (see here), replication is the name of the scientific game bearing in mind how wide the autism spectrum is (the autisms) and the important idea that the label rarely appears in some sort of diagnostic vacuum (see here). I don't believe that we are witnessing a genetic profile for [all] autism just yet...

Before I go, I do also want to comment on at least one area where the genetics of autism seems to be heading: inflammation. As per other research occasions, inflammation and immune function seem to be quite a regular feature of autism genetics studies (see here and see here) and the analysis of more functional biological processes (see here for example). Added to some interesting data on a possible role for those chemical messengers called cytokines with autism in mind (see here) and it looks to me like we have further evidence for how immune function and behaviour might have some interesting connections pertinent to at least some autism (see here).

Music: Amy Winehouse - Back To Black.

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[1] Diaz-Beltran L. et al. A common molecular signature in ASD gene expression: following Root 66 to autism. Translational Psychiatry. 2016. 6, e705.

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Diaz-Beltran L, Esteban FJ, & Wall DP (2016). A common molecular signature in ASD gene expression: following Root 66 to autism. Translational psychiatry, 6 PMID: 26731442