Probiotics for anxiety: fine if you're a (diseased) rodent, but not yet ready for mass roll-out for humans

"While probiotic administration reduces anxiety-like behavior in rodents, the current state of clinical research does not (yet) support probiotics as an efficacious treatment for anxiety."

That was the research bottom-line reported by Daniel Reis and colleagues [1] who scoured the various peer-reviewed science databases looking "to evaluate the clinical and preclinical (animal model) evidence regarding the effect of probiotic administration on anxiety."

Probiotics, in case you don't already know, describe a range of bacteria and yeasts that are touted "as having various health benefits." Most probiotics are taken orally and are thought to be acting on the multitude of wee beasties that in particular, call our gut home (gut microbiota). Anxiety represents a 'state' that manifests as various physical and psychological symptoms. I've talked a lot about anxiety on this blog in the specific context of autism (see here for example) and how absolutely disabling it can be. Mentioning anxiety in the same sentence as probiotics provides a clue that something called the 'gut-brain axis' might be important for some...

Reis et al undertook a systematic review and meta-analysis of the pertinent research literature, having previously published their intention to do so (see here). Randomised-controlled trials matching their inclusion criteria were examined up to November 2017 including both pre-clinical (animal) and clinical (human) studies. The various results were collated, examined and boiled down to a consensus on the basis of the currently available data.

Bearing in mind that the word 'probiotic' covers a lot of ground in terms of what bacteria/yeasts and what preparations are included, the results were a bit of a mixed bag. As mentioned in the opening line to this post, if you're a rodent, the chances are favourable that taking a probiotic might *reduce* anxiety-like behaviour(s). One has to be a little careful about how one defines 'animal anxiety' but compared to placebo, probiotics - specifically including Lactobacillus (L.) rhamnosus - might be something to consider. Even better if you are a 'diseased' rodent...

When it came to the research on anxiety and probiotics in humans, the current status of the research is a little more 'complicated'. So: "Combining standardized mean differences (SMDs) for the 14 included studies revealed a pooled SMD of -0.12, indicating that probiotic administration did not result in a significant reduction of anxiety." The results did not alter where dose and duration were taken into account or whether 'healthy' or 'clinical' participants were observed. Ergo, the current state of the research (up to November 2017) does not generally suggest an action for probiotics in the treatment/management of anxiety in humans.

Of course that does not mean that every study on animals and humans found the same direction (or lack) of effect. We are told that: "At the level of individual trials, 12 of the 22 included animal studies found that probiotics significantly reduced anxiety-like behavior on at least one outcome measure" and "3 of the 14 included clinical studies (encompassing 1527 individuals) found that probiotics significantly reduced symptoms of anxiety." I might also direct your attention to earlier meta-analyses that found that probiotics did seem to affect psychological symptoms in people including anxiety (see here). One therefore needs to be mindful of the limitations of such systematic reviews and meta-analyses and the sweeping generalisations that are made as a result.

But... the results, as they currently stand, suggest that more investigation and perhaps less 'hype' is required around the topic of probiotics for anxiety.

And speaking of meta-analyses over-turning other meta-analyses, I'm not sure I would describe fish oils for a healthy heart as 'nonsense' as one media report did on the basis of a new review. Particularly when other reviews not-so-long ago along similar lines, came to a slightly different opinion with regards to some groups of people...

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[1] Reis DJ. et al. The anxiolytic effect of probiotics: A systematic review and meta-analysis of the clinical and preclinical literature. PLoS ONE. 2018; 13(6): e0199041.

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"... and now believe their pet has canine autism"

A recent tweet from the account of one of the most popular TV breakfast shows here in Blighty made some waves (international waves no less) for a couple of reasons. Leaving aside the insinuation that vaccination *might* correlate with certain behavioural changes in domestic pets, the idea that autism might not be something exclusive to humans was also implied from said tweet.

Needless to say that quite a few people took exception to the idea of 'canine autism'; even the British Veterinary Association (BVA) insisted that "there is currently no scientific evidence to suggest autism in dogs." But is that actually scientifically accurate? And more widely, is it possible for a non-human to have autism or present with significant autistic features?

Before progressing through the evidence around this question, I think it's worthwhile getting a few things straight. First, I appreciate that whilst autism is a label or diagnosis denoting a set of behavioural characteristics that 'significantly impact on day-to-day life' according to current diagnostic schedules, it's also a label of identity for some people. One therefore needs to be sensitive to the effect that discussions about animals also potentially 'having that label' would have to those who associate with an autistic identity. Second, there is a long, very long, history in peer-reviewed research circles, where animals have been used to model aspects of autism. Take for example, the increasingly important research emerging on a role for prenatal valproate exposure as a route to potentially increasing the risk of autism and other neurodevelopmental conditions being diagnosed (see here); an area that has also included discussions of a valproate-treated rodent model of autism (see here) being used in research. Of course, one needs to be aware that modelling autistic features in animals is not the same as autism and all its complexity presenting in humans (including the idea that autism rarely appears in some sort of diagnostic vacuum) and the resulting 'logical fallacies' that can arise (see here). But the assumption is that elements of certain core features of autism can potentially present in non-humans too, and could provide important clues as to the underlying nature of autism.

Going back to that 'no scientific evidence' statement made by the BVA in the lay press, you might be surprised to hear that actually, dogs have been the topic of some research interest in relation to their presenting with some of the features of autism. In an article titled: 'Can Dogs Have Autism?' some of that research was discussed. Starting from an article published way back in 1966 [1] observing behaviour in a dog "resembling human infantile autism" up to more recent peer-reviewed studies [2], several commentators have speculated on facets of autism being present in certain dogs and perhaps being more readily presented in certain breeds of dog. I've actually covered this topic previously in another post on this blog (see here) based on other research [3] reporting on shared biochemical parameters noted in some children and some canines: "tail-chasing Bull Terriers." This, on the basis that from a behavioural and biological point of view, humans are not a million miles away from canines and vice-verse. In short, there is a small scientific evidence base pursuing the notion that facets of autism may present in non-humans too.

Minus too many deep, philosophical musings about our relationship with animals and any evolutionary *connections* between human and animal behaviours, this topic did get me thinking about quite a few other things. It got me wondering whether there may be other behaviours and/or behaviourally-defined conditions / labels that are readily diagnosed in humans but that might also present in non-humans too. I also started to wonder about the myriad of animal-assisted 'interventions' that have been mentioned with autism in mind down the years (see here) and whether other possible research connections could be made as a result. Are we being too presumptuous by saying that the essence of autism is a uniquely human state?

And without trying to trivialise or make light of what autism means to many, many people, there is a long history of speculation when it comes to cats and autism...

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[1] Fox MW. A syndrome in the dog resembling human infantile autism. J Am Vet Med Assoc. 1966 Jun 1;148(11):1387-90.

[2] Zamzow RM. et al. Characterizing autism-relevant social behavior in poodles (Canis familiaris) via owner report. J Comp Psychol. 2017 May;131(2):139-149.

[3] Tsilioni I. et al. Elevated serum neurotensin and CRH levels in children with autistic spectrum disorders and tail-chasing Bull Terriers with a phenotype similar to autism. Transl Psychiatry. 2014 Oct 14;4:e466.

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Therapeutic horseback riding for autism?

"This is the first large-scale randomized, controlled trial demonstrating efficacy of THR [therapeutic horseback riding] for the ASD [autism spectrum disorder] population, and findings are consistent with previous equine-assisted intervention studies."

So said the results of the study by Robin Gabriels and colleagues [1] who, under randomised controlled trial conditions, set about "evaluating the effectiveness of therapeutic horseback riding (THR) on self-regulation, socialization, communication, adaptive, and motor behaviors in children with autism spectrum disorder (ASD)." The authors, including one Gary Mesibov, looked at horse riding vs. barn activities over a 10 week period for a cohort aged 6-16 years old and concluded that under intention-to-treat (ITT) analysis, significant improvements in measures of social cognition and social communication were evident in those following the THR regime. The ClinicalTrials.gov entry for the study can be seen here.

Whilst the methodological quality of the Gabriels study is quite a bit better than anything else so far in this area of investigation, this is not the first time that equine activities have been looked at with autism in mind. The paper by Lanning and colleagues [2] reported a 'favourable outcome' in their small trial "utilizing EAA [equines assisted activities] in the treatment of children with ASD." Similar things were also reported by Bass and colleagues [3] including an important note about less "sedentary behaviors."

Accepting that animal interactions are probably not for everyone on the autism spectrum, the Gabriels and other findings do seem to tie into a growing body of peer-reviewed research suggesting that such interactions might be something to think about when it comes to [some] autism (see here). This also complements other accounts (see here for example). I'm not altogether sure about the hows and whys of animals potentially impacting on the presentation of autism despite previous suggestions about 'parts of the brain' being attuned to animal interactions (see here). One could speculate about animals not perhaps being as socially complicated as people insofar as things like their (general) lack of verbal language for example and the appeal that this would hold. The idea that "animals may act as social buffers for children with ASD" [4] has been banded around. This might, alongside other non-verbal communication variables, also tap into why robots in robot-assisted interventions seem to be also finding some therapeutic favour [5] with [some] autism in mind with lower arousal / stress reduction as a modifying factor.

Whatever the reasons for the potential success behind strategies such as THR and other animal-assisted therapies (where subjected to the appropriate scientific scrutiny) when it comes to autism, one might expect some further research developments in this area. That exposure to animals might also have some hidden 'bacterial' benefits might also be something that autism science should consider particularly in light of emerging data on allergy and atopy with autism in mind...

To close, how could I not link to one of the best horse names ever: hoof-hearted...

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[1] Gabriels RL. et al. Randomized Controlled Trial of Therapeutic Horseback Riding in Children and Adolescents With Autism Spectrum Disorder. Journal of the American Academy of Child & Adolescent Psychiatry. 2015. May 5.

[2] Lanning BA. et al. Effects of equine assisted activities on autism spectrum disorder. J Autism Dev Disord. 2014 Aug;44(8):1897-907.

[3] Bass MM. et al. The effect of therapeutic horseback riding on social functioning in children with autism. J Autism Dev Disord. 2009 Sep;39(9):1261-7.

[4] O'Haire ME. et al. Animals may act as social buffers: Skin conductance arousal in children with autism spectrum disorder in a social context. Dev. Psychobiol. 2015. 27 April.

[5] Diehl JJ. et al. The Clinical Use of Robots for Individuals with Autism Spectrum Disorders: A Critical Review. Res Autism Spectr Disord. 2012 Jan;6(1):249-262.

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Gabriels, R., Pan, Z., Dechant, B., Agnew, J., Brim, N., & Mesibov, G. (2015). Randomized Controlled Trial of Therapeutic Horseback Riding in Children and Adolescents With Autism Spectrum Disorder Journal of the American Academy of Child & Adolescent Psychiatry DOI: 10.1016/j.jaac.2015.04.007

The BTBR mouse and autism

Danger Mouse (from Wikipedia)

It is slightly overwhelming to see the wide range of investigative and research techniques on offer to the modern day scientist when it comes to researching conditions like autism. Indeed, the variety of disciplines and the tools of their trade involved in looking at autism from almost every conceivable research angle, makes it all the more difficult to understand why, at the time of writing, we continue to know so little about autism - aetiology, underlying pathology, etc. - despite such intensive efforts. I'm not here to answer that question by the way; aside that is from mentioning about heterogeneity, comorbidity, genetics-epigentics-environment and the well-trodden path that is 'if you've met one person with autism, you've met one person with autism'.

As per many other conditions / diseases / states, autism research has more than dabbled in the science of trying to establish suitable animal models for the condition as per this review by Paul Patterson* who runs quite a good blog (here). Without wishing to enter into any moral or ethical arguments with anyone about it, quite a few mice, rats, zebrafish and other creatures have met their Maker over the years in the name of autism research. Suffice to say that many more animals are probably going to join them in future; at least more than those who would have been involved in cosmetic research now the European Cosmetics Directive comes into final force (March 2013).

Animal models survive however because of the perceived comparison they can provide where investigations on human beings would not dare to tread. So, inserting genes, deleting genes, controlled exposure to various chemical and drug residues, and lots of other investigations all figure in autism animal research; studies which would not even be entertained to be involving real human beings. The big question though is: how much do such animal models truly tell us about a complex and heterogeneous condition like autism?

Bearing that question in mind, there is one particular animal model of autism which seems to be part of quite a few studies: the BTBR mouse or to give it the full title: the BTBR T+tf/J inbred mouse strain. I should add that I was brought to doing this entry partly following this post on the SFARI website.

Aside from being described as an 'exceptional breeder'(!), the BTBR mouse is of potential interest to autism research because it 'seems' to share quite a few overt behaviours more usually associated with autism spectrum conditions such those involved in social interaction, repetitive behaviours and impairments in play behaviour (see this paper). Even communication by the BTBR mouse has been suggested to some degree, to mirror that seen in autism (here). Throw in indications of 'high anxiety' and it all makes for an attractive animal model of autism.

So what has been noted about this mouse:

• Silverman and colleagues** reported that administration of 2-Methyl-6-(phenylethynyl)pyridine (MPEP), an antagonist for the metabotropic glutamate receptor subtype mGluR5, seemed to reduce the instance of repetitive (self-grooming) behaviour in BTBR mice. Regular readers to this blog might remember my post on glutamate (and glutamine) and autism and some news not so long about about GRN-529 and autism which caused a bit of a stir.
• Frye & Llaneza*** reported on elevations in circulating and brain levels of the neurosteroid, 5α-pregnan-3α-ol-20-one (3α,5α-THP) - a metabolite of progesterone - in the BTBR mouse. The endocrine system has shown more than a passing relationship to cases of autism; be it through the hypothalamus (dopamine, oxytocin, vasopressin) or the link posited between autism and sex hormones (see recent post on PCOS and autism). Dare I even make mention of endocrine disruptors?
• Mercier and colleagues**** indicated the potential presence of connective tissue issues (?) when looking at the anatomy of the meninges in the BTBR mouse. Putting aside my obsession with leaky barriers and autism (and other conditions) and appreciating the difference between the meninges and the blood-brain barrier, I can't help but wonder...
• Heo and colleagues***** reported on elevated levels of anti-brain antibodies amongst other things in relation to immune function of the BTBR mouse. To quote from the authors: "The Th2-like immune profile of the BTBR mice and their constitutive neuroinflammation suggests that an autoimmune profile is implicated in their aberrant behaviors". Inflammation... say no more.
• Finally, I've already talked about the paper by Corley and colleagues****** and their findings of low plasma sulphate (sulfate) in the BTBR mouse (see here) so won't say too much more now.

With the weight of this evidence you can perhaps see why the BTBR mouse might find some favour as a model of autism. There seems to be something for every research palate in among the various studies of the BTBR mouse. I'm certainly not going to poo-poo any comparisons but do have a few minor points to make aside from those already mentioned.

I am genuinely interested in what you might use as a comparator in mouse terms to the BTBR model. Most human studies around autism, certainly interventional or parameter-based, tend to use an asymptomatic control group (hopefully age- and sex-matched) or if you are very lucky, a further group of people with conditions like learning disability or a speech and language disorder (without autism) or the equivalent as comparators. I might be missing important details here but what do you compare an 'autistic mouse' with when ascertaining a specific biological or genetic parameter? Is there such a thing as an 'asymptomatic' mouse or a mouse with learning disability for example or is autism a spectrum of presentation in mice too? (no cheap jokes about systemising mice please).

A further point relates to the something that has cropped up on previous posts in terms of lab mice vs. wild mice and in particular the effects of environment on each as per this article by Boysen and colleagues*******. To quote: "These findings indicate a high degree of pre-activation of NK cells of free-living mice, indicating a strong environmental impact on NK cells, which may be highly relevant for interpretation of studies in the mouse model". In other words, lab mice in their nice sterile, clean-living, environment might not be hardened by the cruel outside world and therefore one questions their representativeness to the real world.

Indeed whilst animal models of 'disease' are the backbone of many a genetic or biological study, there are still some questions about whether they are truly delivering what they promised in terms of translating from lab bench to real-life as per the paper by van der Worp and colleagues******** (full-text) from a few years back. If this is the case, where does this leave the BTBR mouse?


[The picture included in this post will be recognisable to quite a few 'older kids' raised on 1980s UK television. For those who have not had the pleasure of watching Danger Mouse and his sidekick Penfold, here's some more information and that theme tune].

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* Patterson PH. Modelling autistic features in animals. Pediatric Research. 2011; 69: 34R-40R

** Silverman JL. et al. Repetitive self-grooming behavior in the BTBR mouse model of autism is blocked by the mGluR5 antagonist MPEP. Neuropsychopharmacology. 2010; 35: 976-989.

*** Frye CA. & Llaneza DC. Corticosteroid and neurosteroid dysregulation in an animal model of autism, BTBR mice. Physiology & Behaviour. 2010; 100: 264-267.

**** Mercier F. et al. Meningeal/vascular alterations and loss of extracellular matrix in the neurogenic zone of adult BTBR T+ tf/J mice, animal model for autism. Neuroscience Letters. 2011; 498: 173-178.

***** Heo Y. et al. Aberrant immune responses in a mouse with behavioral disorders. PLoS One. 2011; 6: e20912

****** Corley MJ. et al.Reduced sulfate plasma concentrations in the BTBR T+tf/J mouse model of autism. Physiology & Behaviour. April 2012.

******* Boysen P. et al. Natural killer cells in free-living Mus musculus have a primed phenotype. Molecular Ecology. 2011; 20: 5103-5110.

******** van der Worp HB. et al. Can animal models of disease reliably inform human studies? PLoS Medicine. 2010;  7: e1000245.

Animal magic all in the amygdala

Children, generally speaking, are interested in animals. Not all animals and not everyone likes the same animals but show kids a dog, a horse or even an ant crawling on the ground, and it is most likely that you will get some kind of positive response. Take children to a wildlife park or an aquarium and for at least one animal, you can almost see the cogs whirring as they take in this living, moving object in front of them. I've seen it in action many times, most notably on a recent trip to an aquarium and the response to seahorses i.e. bewilderment. Indeed children are often interested in animals that don't even exist anymore. Nearly 20 years after Jurassic Park, dinosaurs and all things dino-related still have the ability to mesmerise (and terrify!).

A recent study by Florian Mormann and colleagues* published in Nature Neuroscience offers some clues as to why humans might be so interested in animals and our potential innate ability to notice and direct our attention to animals. I'm not the first to talk about this study by the way as witnessed by this entry by the BPS Research Digest. Anyhow, the study carried out on 41 patients receiving treatment for drug-resistant epilepsy involved mind-mapping of various parts of the brain. When it came to showing pictures of animals, neuronal activity seemed to peak in the right amygdala of patients; such activity later found not to be related to their participant's epilepsy. The authors concluded that such activity may be evidence for the amygdala as a dedicated part of the brain related to animals as part of our evolutionary relationship with animals as predators and food.

Whilst this was a relatively small study, Mormann and colleagues were very detailed in their examination of the participants involved and their mapping of the brain areas 'lighting up' in response to the animal stimuli over other things like people, landmarks and objects. The amygdala is part of the limbic system which, as described in a previous post on rats being attracted to cats, is thought to be quite an ancient part of the brain evolutionary wise. It perhaps makes sense that we would have a dedicated centre for animal recognition given our close relationship with them down the centuries over relatively new additions to our environment like buildings and everyday objects like telephones and TVs. Who knows in a few thousand years time we might have a dedicated brain centre for things like the computer (in whatever form it takes then).

This work could potentially offer some explanation why animals so strongly feature in relation to many conditions including cases of autism spectrum conditions. Interventions such as hippotherapy (horses not real hippopotamuses), swimming with dolphins and assistance dogs have all, at one time or another, come under the spotlight in relation to autism. I must admit that at times I have been a little 'snooty' about the claims behind individual interventions such as the dolphin therapy; assuming that any child, autistic or not, would probably enjoy some contact with dolphins and questioning how exactly such an experience might long-term affect the presentation of autism. If we are to extrapolate the Mormann findings to these experiences, could there be some kind of connection with the amygdala which has been suggested to show some relationship with autism? Who knows, but it does offer an interesting targets for further research and perhaps puts relationships like the one between Temple Grandin and her cattle-huggers into a new light.

To finish, children growing up in the UK in the 1970s-1980s perhaps will remember one man for making animals our friends, Johnny Morris. Animal Magic.

* Mormann F. et al. A category-specific response to animals in the right human amygdala. Nature Neuroscience. August 2011.