Thursday, 21 February 2019

Serum zonulin testing via ELISA: be very careful

I appreciate that the findings reported by Mary Ajamian and colleagues [1] probably aren't going to set many research hearts racing. Their observations that "current commercial zonulin assays are not detecting the actual protein as prehaptoglobin-2" is not exactly 'change the world' science, but that doesn't mean that they aren't important findings.

So, zonulin is the name of the research game. A protein described with properties "capable of reversible tight junction disassembly and, therefore, is implicated in the regulation of mucosal permeability" means that zonulin and dysregulation of the zonulin pathway has found a home in the science of 'gut permeability' a.k.a leaky gut. And it is with mention of the misnomer called 'leaky gut' and it's *association* with some autism (see here) that I gravitated towards the Ajamian findings. Indeed, zonulin has already made a mark in autism research too (see here). We'll come back to this shortly.

Researchers zoomed in on some of the commercially available methods currently available to 'test for zonulin' - "commercially-available ELISA assays" - and whether they are cutting the scientific mustard. And before I go on I should mention that Ajamian et al aren't the only ones who have looked at this issue [2]. Two ELISA assays were examined: "from CUSABIO (Wuhan, China) and Immundiagnostik AG (Bensheim, Germany)" and pitted against each other and various other analytical techniques to assess "whether the assays are reliably detecting zonulin as prehaptoglobin-2 and if not, what they may be detecting instead." I note the words 'mass spectrometric analysis' are also used in the Ajamian paper, which is music to my analytical ears.

Results: "Serum samples were collected from well-characterised patients and healthy individuals between the ages of 16 and 70 years living in Melbourne, Australia." Those 'well-characterised' participants included those diagnosed with non-coeliac wheat sensitivity (NCWS), coeliac disease, and ulcerative colitis (N=93) and their results were compared with nearly 50 asymptomatic controls. "The majority of study participants were zonulin-producers" as haptoglobin phenotype (see here) was also described in the Ajamian study.

Then to the serum [purported] zonulin levels as measured by those commercial assays: "Compared with the cohort of healthy individuals with a median (IQR) of 0.00 (0.00) ng/mL, patient median (IQR) values for purported zonulin were elevated (all p<0.0001) at levels of 0.032 (0.90) ng/mL in NCWS, 0.07 (1.27) ng/mL in coeliac disease, and 1.73 (2.17) ng/mL in ulcerative colitis" using the CUSABIO assay. Unfortunately, when compared with the other commercial assay (the Immundiagnostik assay), there was apparently little relationship observed between the two when it came to [purported] zonulin levels. And things didn't get any better when for example we are told that "2 of 19 participants who were zonulin non-producers had levels detected by CUSABIO assay."

Various other experiments were carried out and reported on in the Ajamian paper. These included attempts to find out what else might be being picked up by those ELISA assays. Unfortunately, even with the notable analytical prowess of something like mass spectrometry, no definitive compound(s) emerged. Something called complement C3 is discussed, as are other potential matches: "haptoglobin, and albumin." But again unfortunately: "neither complement C3 nor haptoglobin, despite both being candidate target proteins as determined by mass spectrometry, was detected by the CUSABIO assay." So we're not really any further forward when it comes to what might be being detected by such assays.

"In conclusion, the current commercial zonulin ELISA assays investigated in this study detect different proteins, neither of which was zonulin. Therefore, there can be no value of circulating concentrations in assessing intestinal mucosal barrier dysfunction and permeability until the target proteins are indeed identified." A harsh conclusion but faithful to the results observed. What this means is that the literature already published talking about zonulin levels in this, that and t'other label/diagnosis/condition (see here) need to be treated with some caution. And yes, that includes studies that have looked at zonulin levels in autism (see here) and related labels like attention-deficit hyperactivity disorder (ADHD) (see here).


[1] Ajamian M. et al. Serum zonulin as a marker of intestinal mucosal barrier function: May not be what it seems. PLoS One. 2019;14(1):e0210728. Published 2019 Jan 14.

[2] Scheffler L. et al. Widely Used Commercial ELISA Does Not Detect Precursor of Haptoglobin2, but Recognizes Properdin as a Potential Second Member of the Zonulin Family. Front Endocrinol (Lausanne). 2018;9:22.


Wednesday, 20 February 2019

T. gondii infection might be "a contributing causal factor for schizophrenia"

T. gondii mentioned in the title of this post refers to Toxoplasma gondii, a parasite with something of a rather interesting profile and history (see here and see here). I've talked quite a bit on this blog about T. gondii and it's various 'associations', but of particular interest has been the suggestion of a 'connection' between T. gondii exposure and risk of psychiatric diagnoses like schizophrenia (see here).

The findings reported by Kristoffer Sølvsten Burgdorf and colleagues [1] (open-access available here) add further evidence to such a 'psychiatric' connection with their conclusion that: "exposure to T. gondii might be a contributing causal factor for developing schizophrenia." Researchers arrived at their conclusion following the examination of an intriguing initiative called the Danish Blood Donor Study (DBDS). Started in 2010, the DBDS includes records for over 100,000 patients and "contains DNA and EDTA plasma samples, consecutive for all donors returning for blood donation after enrolment." That's a lot of data. So: authors "identified all individuals in the DBDS cohort registered with psychiatric disorders, suicidal behavior, or traffic accidents (N=5,953)." Said participants were matched with 'suitable' controls (N=7,101) and stored samples were analysed for "immunoglobulin (IgG) class antibodies against T. gondii and CMV." CMV by the way, refers to cytomegalovirus. Contact with (congenital) CMV has also been talked about on this blog (see here). CMV (exposure) also shares a potential *link*  with "psychiatric disorders, cognitive deficits, suicidal behavior, and traffic accidents."

Results: "Of the 11,546 studied individuals, 2,990 and 7,020 individuals, respectively, tested positive for IgG class antibodies against T. gondii (25·9%) or CMV (60·8%)." Onward: "We found that individuals with a T. gondii infection had increased odds of being diagnosed with schizophrenia disorders compared to those without infection." Because researchers were also able to access other national databases containing details on outcomes like diagnosis of a psychiatric disorder and 'attempting suicide' and cross-reference them with their participants, they were also able to look at "temporality, with pathogen exposure preceding outcome" as a factor. And when they did, that T. gondii exposure - schizophrenia association was described as "even stronger." The other data on T. gondii or CMV exposure in relation to traffic accidents or suicide attempts was not as statistically strong, and indeed nothing showed significance when temporality was taken into consideration in relation to causation. On that basis, I'm gonna leave that part of the results without further comment.

This was a good study. It drew on data from a well-defined group (those Scandinavian databases 'do it' yet again) and was able to take into account the important issue of temporality. It wasn't a perfect study - "We cannot rule out that socio-economic factors could potentially account for part or all of the observed causal effect" - and said nothing about possible mechanism(s) of effect however. That being said, I'm willing to go along with the conclusions made and the need for a lot more investigation in this area linking T. gondii exposure and subsequent risk of mental illness. In particular whether new or existing treatment methods for T. gondii *might* hold the promise of much more...

And whilst on the topic of T.gondii and the specific input from cats on the spread of T. gondii (see here and see here), I'll state here and now that I am not a great believer in the idea of 'cat eradication' as mentioned by some researchers recently [2]. That being said, a toxoplasmosis vaccines for cats (see here) sounds like a really good idea...


[1] Sølvsten Burgdorf K. et al. Large-scale study of Toxoplasma and Cytomegalovirus shows an association between infection and serious psychiatric disorders. Brain Behav Immun. 2019 Jan 24. pii: S0889-1591(18)30699-8.

[2] de Wit LA. et al. Potential public health benefits from cat eradications on islands. PLoS Negl Trop Dis 13(2): e0007040


Tuesday, 19 February 2019

"people on the autism spectrum have a high prevalence of physical and mental health conditions in midlife and old age"

Should anyone really be that surprised by the findings reported by Lauren Bishop-Fitzpatrick & Eric Rubenstein [1] talking about "a high prevalence of physical and mental health conditions in midlife and old age" when it comes to autism?

Well, yes and no. No, because things like 'psychiatric symptoms and disorders' have already been talked about with regards to older age adults with autism [2] (see here also), alongside various other 'medical comorbidity' being noted in this group (see here). But also yes, because the scale of the physical and mental health conditions identified by Bishop-Fitzpatrick & Rubenstein is quite literally jaw-dropping: "immune conditions (70.6%), cardiovascular disease (49.0%) and its risk factors (46.2%), sleep disorders (85.3%), gastrointestinal disorders (49.7%), neurologic conditions (55.9%), and psychiatric disorders (72.0%) were highly prevalent in our full sample." Said full sample consisted of "de-identified Medicaid claims data for 143 adults with a recorded autism spectrum disorder diagnosis aged 40–88 years."

Researchers also mention how 44% of their sample had an intellectual (learning) disability. This kinda accords with various other data on this topic (see here). Other observations mentioned by the authors also complement existing (peer-reviewed scientific) knowledge that: (a) intellectual (learning) disability seems to bring about an increased risk of epilepsy appearing alongside autism (see here), and (b) depression and anxiety prevalence seems to be particularly elevated in those with autism without any accompanying learning disability (see here) (assuming that depression and/or anxiety are actually being screened for in those with autism + learning disability).

What do the collected data imply? Well, screening is important. Screen and screen and screen and screen. Screen for lots of things, and if something turns up, treat / manage it. If your average Jane or Joe turned up at their Doctors office with a sleep disorder or the symptoms of cardiovascular disease, medical professionals would do something about it. If the Doctor also knew that Jane / Joe might, for example, be more likely than usual to be in receipt of certain classes of medicines that potentially elevates such risks further, they'd be even more keen to screen and intervene. So it should be the same if Joe or Jane is diagnosed with autism or an autism spectrum disorder (ASD).

I'd also suggest that such data should really be leading to a lot more questioning about why? Why do people on the autism spectrum seem to be at particularly high risk of 'immune conditions' or 'digestive disorders'? Are there potential genetic links between autism and such conditions as per the notion that 'autism genes aren't necessarily just genes for autism' (see here) or that such genes might also affect other biological systems as well as the grey-pink matter floating around the skull (see here for example)? Are there other intricate connections between such classes of conditions as per the idea that sleep problems seem to follow gut problems for some (see here)? Why? Pain, discomfort, something else? And don't even get me started on the whole 'immune system - autism' connection (see here for example) which has been known about for many, many, many years. Known about but brushed under the carpet by some.

And whilst talking about the research tag-team that is Bishop-Fitzpatrick & Rubenstein, I once again would direct you to another important paper of theirs [3] about how we need to be very careful about using the word 'comorbidity' when referring to the various mental and physical issues that are over-represented around autism. As we've seen from other research (see here and see here), the core features of autism may very well predispose to a lot more than just autism and, in that respect, this might go way beyond just comorbidity...


[1] Bishop-Fitzpatrick L. & Rubenstein E. The physical and mental health of middle aged and older adults on the autism spectrum and the impact of intellectual disability. Research in Autism Spectrum Disorders. 2019. Jan 29.

[2] Lugo-Marín J. et al. Prevalence of psychiatric disorders in adults with autism spectrum disorder: A systematic review and meta-analysis. Research in Autism Spectrum Disorders. 2019; 59: 22-33.

[3] Rubenstein E. & Bishop-Fitzpatrick L. A matter of time: The necessity of temporal language in research on health conditions that present with autism spectrum disorder. Autism Res. 2019 Jan;12(1):20-25.


Monday, 18 February 2019

"serum levels of certain endocannabinoids are substantially decreased in people with ASD"

The quote titling this post - "serum levels of certain endocannabinoids are substantially decreased in people with ASD [autism spectrum disorder]" - comes from the paper published by Adi Aran and colleagues [1]. It adds to previous study on this topic (see here) and continues a research theme from members of this authorship team where the word 'cannabis' is being discussed - in the peer-reviewed science domain - in the context of [some] autism (see here).

Distinct from the last time authors' research appeared on this blog talking about the feasibility of "Cannabidiol-Rich Cannabis" 'for autism' [2], the name of the research game this time around was to assess "the circulating levels of several endocannabinoids and delineate the correlations between their levels and disease characteristics in a large group of children with ASD and their matched controls with typical development." Researchers mention how previous studies in this area "were not designed to comprehensively characterize the involvement of the ECS [endocannabinoid system] in the pathogenesis of ASD" in quite a sweeping blow to some of the other research in this area.

So, endocannabinoids are part of a system that is involved in various important biological processes [3]. As the name suggests there's an overlap between 'endogenous cannabinoids' and some of the chemical components seen in cannabis that provides as good an answer as any as to why cannabis use/misuse is the continuing issue that it is in a population sense. Authors talk about their study focusing on various endocannabinoids: AEA (anandamide), 2-AG (2-arachidonoil-glycerol), AA (arachidonic acid), PEA (N-palmitoylethanolamine), and OEA (N-oleoylethanolamine). They report how said compounds in serum samples were "analyzed by liquid chromatography/tandem mass spectrometry in 93 children with ASD... and 93 age- and gender-matched neurotypical children." Please don't however get me started on the nonsense that is the word 'neurotypical' (see here). Various other behavioural, psychometric and demographic data were also collected and thrown into the statistical mix.

Results: "Serum levels of the main endocannabinoid AEA and its structurally related compounds OEA and PEA were lower in children with ASD versus age-, gender-, and BMI [body mass index]-matched control group of typically developed children." Nothing particularly new there, as the lower levels of anandamide for example, mimic those reported by Karhson and colleagues [4]. Researchers also mentioned how their findings *might* also have some other potential: "circulating AEA, OEA, and PEA might be used to identify a biologically homogeneous subgroup of ASD, predict response to treatments and adverse reactions to medications, and assist in the development of novel drugs that target specific core symptoms of ASD." Interestingly, some of these 'options' have already been explored [5] in humans and also some animal models [6] with autism in mind.

As to the biochemical *links* between the Aran findings and indeed, the ECS more generally with autism, well, there's still a way to go to decipher them all yet. There are clues emerging [7]; clues that intersect with other important autism-relevant concepts like inflammation among other things. I note also the authors mention how their findings "support the rationale in the ongoing and emerging clinical trials of CBD [cannabidiol] in ASD" (see here) and some results to come.

I'm well and truly [cautiously] interested...


[1] Aran A. et al. Lower circulating endocannabinoid levels in children with autism spectrum disorder. Molecular Autism. 2019; 10:2.

[2] Aran A. et al. Brief Report: Cannabidiol-Rich Cannabis in Children with Autism Spectrum Disorder and Severe Behavioral Problems-A Retrospective Feasibility Study. J Autism Dev Disord. 2018 Oct 31.

[3] Lu HC. & Mackie K. An Introduction to the Endogenous Cannabinoid System. Biol Psychiatry. 2015;79(7):516-25.

[4] Karhson DS. et al. Plasma anandamide concentrations are lower in children with autism spectrum disorder. Mol Autism. 2018 Mar 12;9:18.

[5] Antonucci N. et al. Beneficial Effects of Palmitoylethanolamide on Expressive Language, Cognition, and Behaviors in Autism: A Report of Two Cases. Case Rep Psychiatry. 2015;2015:325061.

[6] Servadio M. et al. Targeting anandamide metabolism rescues core and associated autistic-like symptoms in rats prenatally exposed to valproic acid. Transl Psychiatry. 2016 Sep 27;6(9):e902.

[7] Brigida AL. et al. Endocannabinod Signal Dysregulation in Autism Spectrum Disorders: A Correlation Link between Inflammatory State and Neuro-Immune Alterations. Int J Mol Sci. 2017;18(7):1425. Published 2017 Jul 3.


Saturday, 16 February 2019

Yoga therapy and autism: OK but "better trials are required to confirm the positive impact"

I approach the findings reported by HM Vidyashree and colleagues [1] with my typical critical eye but perhaps also with a sense of 'receptivity' to the idea that yoga training *might* be useful for some people diagnosed as being on the autism spectrum. My receptivity is there because: (a) "yoga is a safe and effective way to increase physical activity, especially strength, flexibility and balance" according to the NHS guide to yoga, and (b) putting aside any (non-testable) spirituality or the like associated with yoga use, I'd like to think that some of the aims of and techniques used in yoga are similar to that seen with some of the martial arts. As well as being a fan of the martial arts - Shotokan karate is my particular hobby - certain martial arts already have some quite positive 'history' in the context of autism in the peer-reviewed science arena (see here and see here for examples). We'll see what we'll see...

The Vidyashree paper had the aim: "to investigate the effect of yoga intervention on short-term heart rate variability (HRV) in children with ASD [autism spectrum disorder]." HRV is basically what it describes: "a measure of the variation in time between each heartbeat." That variation is controlled by something called the autonomic nervous system (ANS), which basically regulates various bodily functions typically minus conscious input from ourselves. From what I gather, a low HRV is something to be avoided; as people talk about a higher HRV being linked to better cardiovascular fitness as well as increased resilience to stress (whatever that means). You probably won't be surprised to hear that HRV has been previously talked about with autism in mind [2], albeit with a lot more investigation required (see here).

So: "50 children (38 boys and 12 girls) with ASD were recruited from Swabhimaan Trust, Palavakkam, Chennai." All were diagnosed with an autism spectrum disorder (ASD) and "were grouped into ASD with yoga intervention (n = 25) and ASD without yoga intervention group (n = 25) by simple lottery method." HRV was recorded via an ECG (electrocardiogram) on two occasions, before and after intervention/non-intervention. Said yoga intervention - in 40 minute sessions - was apparently delivered "every day in the morning" over 3 months. That's quite a few sessions...

Results: bearing in mind 10 participants and 5 participants from the yoga and non-yoga groups respectively were excluded from the data analysis side of things, a few details were observed. So: "There is a significant reduction in mean HR [heart rate]... in the ASD children after yoga intervention." As a group, the mean baseline HR for the yoga group was around 90 beats per minute. After intervention, this dropped to under 80 beats per minute. At the same time, the non-yoga group showed an increase in their mean heart rate over the same period. Other results, more technical results, are also included in the Vidyashree paper which I believe translate into measuring HRV [3]. I can't pretend to know all the hows-and-whys of those results, but with a cursory reading of the literature in this area, am willing to go along with the authors' conclusions that results: "showed significant improvement" coinciding with the yoga intervention.

Obviously a lot more study is required in this area before any grand claims about yoga or anything else are made in the context of autism. The Vidyashree results were firmly focused on HRV following yoga and said nothing about how yoga may/may not have affected some of the behavioural profiles associated with autism for example. Likewise, all the stuff about lower HRV being linked to greater resilience to something like stress have not been fully analysed in the context of the current results either. All of this comes alongside the methodological issues that accompany the Vidyashree: an open-trial, yoga vs. no yoga, etc.

But I still remain interested in the potential of something like yoga in many contexts including that related to autism...


[1] Vidyashree HM. et al. Effect of Yoga Intervention on Short-Term Heart Rate Variability in Children with Autism Spectrum Disorder. Int J Yoga. 2019;12(1):73–77.

[2] Daluwatte C. et al. Atypical pupillary light reflex and heart rate variability in children with autism spectrum disorder. J Autism Dev Disord. 2013 Aug;43(8):1910-25.

[3] Shaffer F. & Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Front Public Health. 2017;5:258. Published 2017 Sep 28.


Friday, 15 February 2019

Regression and autism: "The regression group was significantly more functionally impaired..."

The quote forming part of the title of today's post - "The regression group was significantly more functionally impaired..." - comes from the findings reported by Lucy Thompson and colleagues [1] (open-access available here). It continues something of an important theme in autism research circles whereby regression, as in a regression of previously acquired skills, is being seen as important not just for a few but for many (see here).

There were a few aims to the Thompson study such as establishing "the relative prevalence of regression in autism" and "possible predictors, mediators and moderators of regression in autism, including pre- and perinatal factors." The data for the study were derived from "two community-based cohorts" in Sweden totalling just over 300 participants (children) diagnosed with an autism spectrum disorder (ASD) who were observed over two different time points (T1 and T2 2 years later). Another important detail is mentioned by Thompson et al: "Given the lack of previous systematic representative studies in the field, our study sets out to be descriptive rather than hypothesis-driven." Figures and details on regression in the cohort(s) were obtained via specific questioning on this topic "defined as loss of expressive language skills (loss of 5 or more words that had been used communicatively) in connection with the onset of autism." This data was also combined with other medical records information to determine 'consistency'.

Results: "Just over 20% (62/303) of the combined sample of children had regressive autism." That's 1 in 5 children with autism experiencing some kind of regression in relation to language skills. When looking at those who regressed (n=62) compared with those with no regression (n=241), a few details emerged: "Those with regressive autism had a younger age when they first walked... had a more severe language impairment at T1... and more often intellectual disability... [and] lower mean VAB [Vineland Adaptive Behaviour Scales-IIscores." Also: "Severity of autism was higher in the regressive group, with a higher proportion of children with autism... (as opposed to autistic-like condition)."

This is important data. It kinda tallies with other studies of regression accompanying autism suggesting that those who regress tend to have a more 'severe' form of autism with accompanying learning (intellectual) disability. The diagnostic issues - as in more likely to be diagnosed with Kanner's autism rather than other diagnoses - similarly ties in with other findings.

Caveats? Well, a few: "We have chosen to focus on language regression specifically (rather than social, play or motor regression) as communication is by far the most common skill to be lost or diminished in regressive autism." That being said, regression accompanying autism seems to take many, many forms and does not always just mean a loss or partial loss of vocal communication (see here).

Also: "There was also a similar level of maternal disease in pregnancy in the regressive and non-regressive groups, suggesting that prenatal exposure via maternal disease does not seem to be a key feature in the development of regressive autism." I have to question why the authors stuck to looking at just pre- and perinatal factors as possibly being *linked* to regression when regression is likely to occur quite some time after such a developmental window. Surely it would have made more sense to ask a few further questions about the timing of regression - "The average age at regression was 20.13 months... with 54 children (88.5%) showing regression by the age of 24 months" - and whether one or more event might have proceeded such regression in a similar time frame. Y'know whether infection might be a feature (see here and see here for examples) or whether other events might require further investigation (see here). I know this might take such research down some uncomfortable paths, but temporality is surely an important factor for some regression in some cases of autism? Or am I being too unreasonable?

I might also advance the idea that the time to start asking questions about the biology of regression accompanying autism is fast approaching. We've already had some clues in the recent (at the time of writing) peer-reviewed research literature (see here) but lots more needs to be done in this area. Are there important genetic and/or epigenetic variables to consider? Do mitochondrial issues play a role in some regressive autism (see here)? We just don't know enough yet. And yes, this does mean also asking about whether regression in behaviour or cognitive skills was also accompanied by any changes to somatic variables too (see here).

And then there is another question to ask/answer: does regression mean that certain 'therapeutic' options might be particularly useful? I'm thinking back to some research a few years back talking about corticosterioid therapy *potentially* being indicated for some cases of regressive autism (see here). No, I'm not making any medical or clinical claims or giving any advice on such an issue. Merely mentioning that regressive autism needs to be more of a research priority than it currently is. To quote Thompson and colleagues again: "Children with a regressive developmental trajectory, with or without autism, always need a careful neuropediatric work-up to investigate possible neurological disorders that may lead to developmental regression, taking into account possible treatable conditions." Who would argue with that?


[1] Thompson L. et al. Autism With and Without Regression: A Two-Year Prospective Longitudinal Study in Two Population-Derived Swedish Cohorts. J Autism Dev Disord. 2019 Feb 4.


Thursday, 14 February 2019

The gut microbiome and autism... so far (continued)

Building on other reviews of the peer-reviewed science literature looking at the intestinal microbiota in relation to autism (see here), the paper published by Feitong Liu and colleagues [1] provides an updated 'where we're at' position in relation to the "potential evidence for the characteristic dysbiosis of gut microbiota in ASD [autism spectrum disorder] patients compared with healthy controls (HCs)." Just before you say anything, those are the authors words not mine; I'm not a fan of the word 'patients' nor use of the term 'healthy control' to denote not autism - not autistic, but there you go.

Language use aside, the Liu paper covers quite a lot of the peer-reviewed science talking about gut bacteria and autism up to March 2018. Their systematic review took in data from 16 studies - human studies "that compared the composition of gut microbiota in ASD patients and HCs using culture-independent techniques." Researchers had also previously registered their intention to conduct this review as per their PROSPERO entry (see here).

So what did their systematic review reveal? Well, they talked about how most studies looked at the intestinal microbiota via the examination of stool samples, although a couple relied on gut biopsy samples instead. Coincidentally, I spotted a bit of an error in the Liu paper in relation to their study reference numbering in one of the results sections, and how the Luna study (see here) and Williams study (see here) which relied on biopsy samples were replaced by other 'stool as a sample media' studies in the Liu write-up. It's only a small point and doesn't detract from the paper overall. The included studies also covered various different populations in a geographic sense as well as taking into account a mix of participants (with autism) in terms of the presence of gastrointestinal (GI) issues and the use of 'special' diets. Indeed, we are told that: "As restricted diet is very common in ASD patients, we tried to extract the information of eating habit in ASD and control group." Yes it is common, and yes it can have sometimes very negative effects (see here). Finally, all the studies included for review were "identified and assessed as medium (6–7) to high (8) quality" suggesting that the data were pretty reliable in a methodological sense.

Some key points emerged: "Overall, the changed structure of gut bacterial community in terms of β-diversity was observed coherently in ASD patients compared with HCs." Beta-diversity basically translates into 'between samples diversity' and in this case represents autism vs. not-autism controls. Out of the 16 studies included in their systematic review, Liu et al reported that "ten studies analyzed β-diversity (unweighted UniFrac distance, weighted UniFrac distances, and Bray-Curtis)." Six of those 10 studies "consistently reported that the microbiota of ASD patients clustered significantly apart from that of HCs." Ergo, there is evidence - some evidence - that the gut microbiome is significantly 'different' in autism compared with not-autism in a group sense. Some evidence at least.

Also: "Consistently, ASD patients had elevated abundance of Proteobacteria rather than HCs. In addition, Bifidobacterium, Blautia, Dialister, Prevotella, Veillonella, and Turicibacter were consistently decreased, while Lactobacillus, Bacteroides, Desulfovibrio, and Clostridium were increased in ASD patients relative to HCs."  Bear also in mind that Liu et al talked about various other bacterial species that were, in individual studies, elevated or depressed in the groups with autism, and how important such information might be. Such bacterial changes in terms of diversity or individual species predominating might also have knock-on effects as a result of the different chemical messages that different bacteria produce. One example: "Bacteroides is an abundant genus at all ages, from infants to adults. It is the main producer of propionate in the gut, and the abundance of propionate in feces correlates strongly with the abundance of Bacteroides." It probably won't surprise you to hear that propionic acid (propionate) has also got some research history when it comes to autism (see here) and indeed, with caveats, continues to do so [2]. Other examples are included in the Liu paper, including the 'chemical of the moment', butyrate (butyric acid) (see here). This complements other recently published research [3] too. And let's not forget how such bacteria and their chemical messaging also has some important 'effects' on things like gut barrier function and gut immune function, as part of the 'new triad' when it comes to autism and the gut (see here).

"Microbiome reconstitution could be a potential therapy to ASD patients in future." That's another topic raised in the Liu study on how "remodeling gut microbiota with diet, antibiotics, prebiotics, probiotics, and FMT [fecal microbiota transplant]" could be an option. Actually the future is now, as a quick scour of the autism research literature shows that some of these options are already being / have been investigated (see here and see here for examples). We do need a lot more information on the hows-and-whys of such therapeutic options; importantly covering safety, effectiveness and maybe highlighting the possible mechanisms involved, but there is already existing literature in this area.

As well as highlighting some of the shortcomings of the current research literature discussing the intestinal microbiota and autism, the Liu study provides a nice overview of this topic as things currently (up to March 2018) stand. Whether such information can eventually be 'manipulated' to improve things like quality of life in the context of autism remains to be seen...


[1] Liu F. et al. Altered composition and function of intestinal microbiota in autism spectrum disorders: a systematic review. Translational Psychiatry. 2019; 43.

[2] Shams S. et al. Systemic treatment with the enteric bacterial metabolic product propionic acid results in reduction of social behavior in juvenile rats: Contribution to a rodent model of autism spectrum disorder. Dev Psychobiol. 2019 Jan 28.

[3] Wang M. et al. Alterations in Gut Glutamate Metabolism Associated with Changes in Gut Microbiota Composition in Children with Autism Spectrum Disorder. mSystems. 2019 Jan 29;4(1). pii: e00321-18.