Thursday, 22 March 2018

On mitochondrial DNA (mtDNA) changes and autism

Mitochondrial issues accompanying some diagnoses of autism have quite a bit of peer-reviewed research backing (see here for example). Not for everyone, but for some people diagnosed with an autism spectrum disorder (ASD), there seems to be something afoot with regards to these 'powerhouses of the cell' that could well impact on various aspects of their lives [1]. Indeed, keep that paper from Poling et al [1] in mind...

Although by no means an expert on mitochondrial issues in any context, I believe that there are a few ways in which mitochondrial dysfunction can manifest. It can present as a secondary disorder for example (see here), where some acquired biochemistry (non-genetic) provides some of the 'answers'. Or it can present as a primary mitochondrial disorder, a genetic condition "confirmed by a known or indisputably pathogenic mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) mutation" [2], where issues in the genetic code of mitochondria are present.

The recent findings reported by Noémi Ágnes Varga and colleagues [3] focused on that latter route looking at issues with mtDNA in the context of autism. They turned up some rather interesting results...

So: "The aim of the present study was to investigate the presence of the most common pathogenic mtDNA alterations in patients with ASD." Researchers screened 60 children with autism and 60 not-autism controls. One detail stuck out when it came to those controls: "Our control group for mtDNA screening consisted of 60 European adults (26 females and 34 males, median age = 28 years, IQR = 13.75) selected from our biobank." Compared with those participants diagnosed with autism, they were quite a bit older (median age = 7 years vs. median age  = 28 years) and indeed, the gender ratios were a little bit more balanced.

Anyhow: "Mitochondrial deletions were identified in 16.6% (10/60) of our patients with ASD." OK, 'patients' is not exactly the word I would use for participation in such a research project but that shouldn't distract from the findings. Varga et al also provide some further insights into those 10 'participants' with a diagnosis of autism and mtDNA deletion(s) which turned up some other interesting details, such as the finding that various other symptoms presented alongside autism. Quite a few of them were connected to muscle and movement functions (limb and truncal ataxia, hypotonia, dyspraxia) which ties into other independent findings [4]. I also noted the words 'gluten sensitivity' were mentioned in one case, which is guaranteed to perk my professional interest (see here) although I'm still a little unsure of whether this connected to mtDNA issues or not.

Another set of potentially important details were also observed by researchers when comparing those with autism with and without mtDNA deletion(s). Keeping in mind the small numbers falling into that autism with mtDNA deletion(s) category, developmental regression seemed to be an important facet of the clinical profile of this group. Regression of previously acquired skills is something else I've talked about quite a bit on this blog with regards to autism (see here and see here for examples). Going back to that paper by Jon Poling and colleagues [1] that I told you to keep in mind, it's interesting to note the overlap of regression reported by them and also reported by Varga in the context of mitochondrial disorder. And this isn't the only occasion that regression and mitochondrial issues have been talked about in the same breath as autism [5] and even with other potentially important clinical indicators [6]. Correlation is not necessarily causation but...

There are quite a few other details listed in the Varga paper that I'd encourage readers to pursue but I think I've gone on enough about this topic for now. It, yet again, appears that a diagnosis of autism is protective of nothing when it comes to other conditions/diseases/symptoms/labels appearing and perhaps implies that preferential screening for mitochondrial disorder should be more commonplace than it is as and when autism is diagnosed. I'm also inclined to draw your attention to other clinical labels where mitochondrial issues might be relevant for some (see here) albeit not always with genetics in mind (see here). How perhaps investigations need to be carried out looking at any possible intersection between *some* autism and something like myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) (see here) for example, also in light of other important data (see here). Indeed, I'll be coming to the findings reported by Bilevicute-Ljunger and colleagues [7] on this topic quite soon in a separate post...

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[1] Poling JS. et al. Developmental Regression and Mitochondrial Dysfunction in a Child With Autism. J Child Neurology. 2006;21(2):170-172.

[2] Niyazov DM. et al. Primary Mitochondrial Disease and Secondary Mitochondrial Dysfunction: Importance of Distinction for Diagnosis and Treatment. Mol Syndromol. 2016 Jul;7(3):122-37.

[3] Varga NA. et al. Mitochondrial dysfunction and autism: comprehensive genetic analyses of children with autism and mtDNA deletion. Behavioral and Brain Functions. 2018. 14: 4.

[4] Ghaoui R. & Sue CM. Movement disorders in mitochondrial disease. J Neurology. 2018. Jan 6.

[5] Rossignol DA. & Frye RE. Mitochondrial dysfunction in autism spectrum disorders: a systematic review and meta-analysis. Mol Psychiatry. 2012 Mar;17(3):290-314.

[6] Shoffner J. et al. Fever plus mitochondrial disease could be risk factors for autistic regression. J Child Neurol. 2010 Apr;25(4):429-34.

[7] Bilevicute-Ljunger. I. et al. Patients with chronic fatigue syndrome do not score higher on the Autism-apectrum quotient than healthy controls: comparison with autism spectrum disorder. Scandinavian Journal of Psychology. 2018.

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