passionless Droning about autism

Archive for the ‘Feedback Loops’ Category

Hello friends –

Whatever your take on the predominant cause of autism(s), your thoughts on the appropriateness, or inappropriateness of research allocations in the autism realm, one thing can’t be denied; collectively, a lot of researcher time and dollars have been poured into autism research.  We’ve learned some important things, some cool things, some confusing things, some obscure things, and some useless things.   But even with all of the resources we have applied towards understanding autism, one of the most curious unknowns is also one obvious to the most rudimentary observations, the persistently skewed male to female ratio, with a finding of three or four males to every female with autism.   It is one of the most vexing questions, almost taunting us with seeming obviousness, but consistently elusive.  It isn’t just autism, lots of other neurological conditions are similarly tilted, and in a bazillion animal models it seems an unfortunate fact that being born male simple predisposes you (or rat you) to a variety of things you’d rather not have. 

The ideas I have seen floated most frequently to explain this observation involve the effect of prenatal testosterone and the associated ‘extreme male brain’ theory, a loss of genetic backups to compensate for mixups, and synergistic effects of testosterone on chemicals, notably, mercury; explanations which I generally like a little, a little less, and almost not at all, respectively.  An idea I’ve floated a couple of times, but that seemed even less accepted (or, more likely, completely unnoticed), was that estrogen might be acting in a protective manner; as it is known to exhibit attenuate the effects of neuroinflammation and oxidative stress.  Indeed, it is starting to look like estrogen receptors are expressed in a large variety of situations salient to CNS processes.  

A few weeks ago, the same group that has published some immensely cool studies on epigenetics and brain proteins, genetic expression differentials within twin siblings with autism, and circadian rhythm alterations comes a paper which may give us insight into this question, so that is pretty exciting.  Even cooler, it invokes a negative feedback loop in a complicated system and is built upon the foundation of several earlier studies on a protein implicated in lots of things we know are awry in autism.  That study is Sex Hormones in Autism: Androgens and Estrogens Differentially and Reciprocally Regulate RORA, a Novel Candidate Gene for Autism (full paper).  Here is the abstract:

Autism, a pervasive neurodevelopmental disorder manifested by deficits in social behavior and interpersonal communication, and by stereotyped, repetitive behaviors, is inexplicably biased towards males by a ratio of ~4:1, with no clear understanding of whether or how the sex hormones may play a role in autism susceptibility. Here, we show that male and female hormones differentially regulate the expression of a novel autism candidate gene, retinoic acid-related orphan receptor-alpha (RORA) in a neuronal cell line, SH-SY5Y. In addition, we demonstrate that RORA transcriptionally regulates aromatase, an enzyme that converts testosterone to estrogen. We further show that aromatase protein is significantly reduced in the frontal cortex of autistic subjects relative to sex- and age-matched controls, and is strongly correlated with RORA protein levels in the brain. These results indicate that RORA has the potential to be under both negative and positive feedback regulation by male and female hormones, respectively, through one of its transcriptional targets, aromatase, and further suggest a mechanism for introducing sex bias in autism.

The press release and google news cycle for this paper seemed to have been well ahead of the pubmed robot; Kev had a post on this study a few weeks before it hit pubmed with a postdate.  I generally skip out on the interest story/vaccine fairytale story/vaccine nightmare story/lost child nightmare story that is the google news autism feed, but in this case, it harbored a story on a paper that I was actually interested in.  In any situation, the paper landed in pubmed this morning, and is available in full via PLOS, so great stuff is available to us all.

The paper starts with some of the backstory, the ‘inexplicable’ male predominance in autism, some of the theories on why this might be the case, and most importantly, details on previous findings by this set of researchers on reduced levels of RORA in the CNS of people with autism, a protein with a great number of functions of interest to the autism community.

Together, these results link molecular changes in RORA in peripheral cells to molecular pathology in the brain of autistic individuals. These findings are particularly relevant to ASD as RORA is involved in several key processes negatively impacted in autism, including Purkinje cell differentiation, cerebellar development, protection of neurons against oxidative stress, suppression of inflammation, and regulation of circadian rhythm. Behavioral studies on the RORA-deficient staggerer (RORA+/sg) mouse, primarily used as a model to study ataxia and dystonia[13], further show that RORA is also associated with restricted behaviors reminiscent of ASD, such as perseverative tendencies, limited maze patrolling, anomalous object exploration as well as deficits in spatial learning.

It’s tough to find a protein with a greater key word hitlist for our population of interest than Purkinje cell differentiation, cerebellar development, protection from oxidative stress, suppression of inflammation, and regulation of the circadian rhythm.  In fact, I’d be shocked to find a protein touching so many fracture points that wasn’t found altered in the autism population; it makes too much sense within the framework of an entangled system and what we already know about the physiology of autism.   Remember that the previous paper found decreased RORA in the brain of people with autism; i.e., less of a protein that protects from oxidative stress, supports Purkinje cell development, and suppresses the inflammatory response.  A relative lack of RORA makes a depressingly good amount of sense. 

That being said, what makes the current paper so interesting is that they found the RORA is differentially, and inversely modulated by female and male hormones (i.e., testosterone and estrogen).  But even more insidiously, one of the downstream products regulated by RORA, aromatase, participates in the cleavage of testosterone to estrogen; the authors essentially describe a negative feedback loop.  It turns out, not only is RORA decreased in the CNS of autism, but so too is aromatase. 

We also show that one of the transcriptional targets of RORA is aromatase, which is a crucial enzyme in the biosynthesis of estrogen from testosterone. It is noteworthy that both RORA and aromatase proteins are decreased in the frontal cortex of autistic subjects, and that the level of aromatase protein is strongly correlated with the level of RORA protein in the brain tissues. We therefore propose that the reduction of RORA observed in autism is exacerbated by a negative feedback mechanism involving decreased aromatase level, which further causes accumulation of its substrate, testosterone, and reduction of its product, estradiol. Testosterone and estradiol respectively exhibit negative and positive feedback regulation of RORA expression as illustrated in Fig. 5, which summarizes the principal findings of this study. Thus, a deficiency in RORA in autistic brain is expected to be further aggravated by increased levels of testosterone due to suppression of aromatase, a transcriptional target of RORA.

This is pretty neat; it shows how simply being male can lead to the downregulation of a system with tendrils attached to a great number downstream processes we know to be disturbed in autism. 

I particularly liked that this paper established a chain of learning more, something I think we can all agree is a great idea.  Some of the people on this study have been plugging away with some interesting ideas for a while, all of which, I believe, are ancestors of these findings.  They had two really neat papers on genetic expression in autism twins with differential degrees of autism severity, both of which used genomic bioinformatic tools to understand which the genetic pathways were affected.  This is actually rather brilliant; they essentially leveraged the genetic uniqueness of the twins to gain more insight into which processes were being affected in autism by seeing which genes were differentially expressed in identical twins that manifested differently, using genetics to learn about what is happening a layer above the genome.  Next, the original RORA paper began to probe the mechanism by which the previously observed expression was achieved, they found that a particular protein, RORA, was overmethylated and consequently at depressed levels.  Another bioinformatic approach told them that RORA was a particularly attractive candidate for further evaluation based on its descendant interactions, and the association between RORA, aromatase, and sexual hormones appeared.  Beautiful.

All that coolness not withstanding, some of the articles I saw on this lacked the caution and nuance we ought to see with these kinds of findings; the paper was pretty clear that previous CNS studies hadn’t shown decreased RORA in all of their samples, just most of them.   This doesn’t answer all of our questions about the male dominance of autism, but we do know more than when this study was published, and that is pretty cool.   Hooray for knowledge.

    pD

Hello friends –

Hot on the heels of Mitochondrial Dysfunction in Autism, another study on mitochondrial function in the autism population was just released, this time giving us insight into what is happening inside the gated community behind the blood brain barrier.  How potentially inconvenient.  Brain region-specific deficit in mitochondrial electron transport chain complexes in children with autism came out the other day; I’ve yet to receive a full copy (one has been promised to my real world email), but the abstract is juicy enough to warrant a small posting.

Mitochondria play important roles in generation of free radicals, ATP formation, and in apoptosis. We studied the levels of mitochondrial electron transport chain (ETC) complexes, i.e., complexes I, II, III, IV, and V, in brain tissue samples from the cerebellum and the frontal, parietal, occipital, and temporal cortices of subjects with autism and age-matched control subjects. The subjects were divided into two groups according to their ages: Group A (children, ages 4-10 years) and Group B (adults, ages 14-39 years). In Group A, we observed significantly lower levels of complexes III and V in the cerebellum (p < 0.05), of complex I in the frontal cortex (p < 0.05), and of complexes II (p < 0.01), III (p < 0.01), and V (p < 0.05) in the temporal cortex of children with autism as compared to age-matched control subjects, while none of the five ETC complexes was affected in the parietal and occipital cortices in subjects with autism. In the cerebellum and temporal cortex, no overlap was observed in the levels of these ETC complexes between subjects with autism and control subjects. In the frontal cortex of Group A, a lower level of ETC complexes was observed in a subset of autism cases, i.e., 60% (3/5) for complexes I, II, and V, and 40% (2/5) for complexes III and IV. A striking observation was that the levels of ETC complexes were similar in adult subjects with autism and control subjects (Group B). A significant increase in the levels of lipid hydroperoxides, an oxidative stress marker, was also observed in the cerebellum and temporal cortex in the children with autism. These results suggest that the expression of ETC complexes is decreased in the cerebellum and the frontal and temporal regions of the brain in children with autism, which may lead to abnormal energy metabolism and oxidative stress. The deficits observed in the levels of ETC complexes in children with autism may readjust to normal levels by adulthood. (my emphasis)

A few things immediately jump out at me.  Firstly, the Chauhan’s are authors of this paper, who have been around the autism / oxidative stress block since the get go, as authors of the very nice Oxidative stress in autism: increased lipid peroxidation and reduced serum levels of ceruloplasmin and transferrin–the antioxidant proteins, a really nice paper that was one of the first I saw that broke the autism groups into classic and regressive phenotypes with findings of increased oxidative stress in the latter.

Secondly, one of the biggest concerns with Mitochondrial Dysfunction in Autism when it was released a few weeks ago was, whether or not the findings taken from lymphocytes, cells outside of the brain, could be reliably used as proxies for what is happening within the CNS.  Based on the findings in Brain region-specific deficit in mitochondrial electron transport chain complexes in children with autism it would seem that, at least in children, there is an increased frequency of mitochondrial problems in the brain.  Of course, if we acknowledge the reality of the interconnectedness of immune activation, oxidative stress, mitochondrial impairment and what we already know about the CNS in autism, these findings shouldn’t really be all that surprising.  None the less, it is nice to have some direct evidence of this.

Unfortunately, we still don’t know what is causing the problems with mitochondria function in the brain; it is possible, though exceedingly unlikely that all of the participants in this study also had a diagnosable electron chain disorder (I haven’t gotten a full copy of the paper yet).  I think it is possible that there is a feedback loop in place involving the immune response, oxidative stress, and mitochondria that for some reason our children’s physiology cannot shake loose from. 

The very small sample size of the children in this study, five, is an unfortunate reality for nearly all brain based studies in the autism world.  Though I’ve yet to read the full paper, my prediction is that it is liberally peppered with cautious language regarding interpreting the findings widely without further confirmation.  That is probably pretty good thinking.

But, if we look closely, and we taken notice of the where of mitochondrial problems in the autism group was observed, we may have evidence of participatory processes.  Specifically, Chauhan found decreased electron chain transport measurements in the cerebellum, frontal cortex, and temporal cortex.

In Group A, we observed significantly lower levels of complexes III and V in the cerebellum (p < 0.05), of complex I in the frontal cortex (p < 0.05), and of complexes II (p < 0.01), III (p < 0.01), and V (p < 0.05) in the temporal cortex of children with autism as compared to age-matched control subjects, while none of the five ETC complexes was affected in the parietal and occipital cortices in subjects with autism.

(my emphasis)

There have been a few other studies (that I know of) that have looked for brain region specific abnormalities that might be of interest to u.  Brain Region-Specific Changes in Oxidative Stress and Neurotrophin Levels in Autism Spectrum Disorders (ASD), which found increased markers of oxidative stress in the cerebellum:

Consistent with our earlier report, we found an increase in NT-3 levels in the cerebellar hemisphere in both autistic cases. We also detected an increase in NT-3 level in the dorsolateral prefrontal cortex (BA46) in the older autistic case and in the Wernicke’s area and cingulate gyrus in the younger case. These preliminary results reveal, for the first time, brain region-specific changes in oxidative stress marker 3-NT and neurotrophin-3 levels in ASD.

(My emphasis)

Interesting note: the ‘Wernicke’s area’ of the brain plays a large part in language skills, and in fact, damage to the Wernicke’s area can cause a type of aphasia. 

The number of studies that tie together oxidative stress and mitochondrial function are many and numerous to the point of cumbersomeness, I have a short list of them on a previous post about mitochondria function in autism, here

Two of the really nice neuroimmune studies in the autism realm, Neuroglial Activation and Neuroinflammation in the Brain of Patients with Autism, and Immune Transcriptome Alterations In the Temporal Cortex of Subjects With Autism both provide evidence of an ongoing immune response in some of the specific areas of the CNS where Chauhan found impaired mitochondrial function, the cerebellum and the temporal cortex.

From Vargas:

We demonstrate an active neuroinflammatory process in the cerebral cortex, white matter, and notably

in cerebellum of autistic patients.

And

The neuroglial activation in the autism brain tissues was particularly striking in the cerebellum, and the changes were associated with upregulation of selective cytokines in this and other regions of the brain.

 

From Garbett:

 

Expression profiling of the superior temporal gyrus of six autistic subjects and matched controls revealed increased transcript levels of many immune system related genes. We also noticed changes in transcripts related to cell communication, differentiation, cell cycle regulation and chaperone systems.

 

Detangling if these findings are related, and if so, the direction of causality is for another series of studies to discern.  Calls towards the possibility that relationships like this are spurious are common, but I hate to invoke coincidences for no good reason other than coincidences do occur.  My suspicion is that the immune findings and impaired mitochondria findings are related, but a cautious suspicion is all that is warranted at this time.  I do believe that the relationship between immune activation and mitochondria function is being evaluated now; though I do not know if it is being addressed directly in the CNS, which would be ideal.

 

Curiously from my perspective, however, is the finding that young adults and adults with ASD in Chauhan did not exhibit decreased electron chain function.  The original microglia paper from Vargas, Neuroglial Activation and Neuroinflammation in the Brain of Patients with Autism found extensive evidence of an ongoing immune response in the CNS of people with autism into adulthood.  From the standpoint of a theory wherein an immune response were driving the mitochondrial impairment due to increased oxidative stress, the findings in Chauhan of normal mitochondria function are contradictory to what was found in Vargas.  (?) 

 

A few other thoughts occurred to me as I considered the age differences found in Chauhan.  If mitochondrial dysfunction is part of the pathogenic force driving behaviors associated with autism, it is possible that a decrease as adulthood is reached conforms with a general improvement in adaptation many people seem to report.  Alternatively, if we are actually observing a true increase in the number of people with behaviors that can be classified as autistic, that is, the number of children with autism is a new phenomena, the age findings in Chauhan could be artifacts of different underlying causes of autism in the adults versus the children.  I’m a big believer in a wide range of physiological roads to the end point of autistic behaviors, so such a situation doesn’t really bother me conceptually, though it is very, very problematic to put to any kind of designed experiment. 

 

Lastly, for a while now I’ve been putting some thought towards something that’s really been bugging me about the neuroimmune findings in autism when put in context with other ‘classic’ neurological diseases that also exhibit a strong immune component; i.e., Alzheimer’s or Parkinson’s, both of which have strong immune findings as well, but are more strikingly degenerative in nature when compared to autism.  Generally you talk about a child with autism gradually getting better, or in some cases reaching a plateau; but very rarely (or never) is there the steady and unforgiving decrease in function that you see in diseases like Alzheimer’s.  I’m struggling with this reality and how our findings fit in.  I’m not sure how, or if, the age differences in Chauhan are meaningful towards this apparent paradox, but my pattern recognition unit sure is trying to tell me something, I just can’t tell if it’s sending me on (another) snipe hunt or not.

 

When the entire paper lands in my inbox, I may write another post about it.  I’m interested in seeing if any other blogs pick up on this paper or not and what their take on it is.  I’m still sort of in the dark on the machinations of the press cycle as it relates to autism news, but this paper doesn’t seem to have gotten the press release treatment that Mitochondrial Dysfunction in Autism did, even though its findings are just as interesting. 

 

          pD

Hello friends –

The mitochondria discussion in the autism community reminds me a lot about the political discussion in the United States; I know it is important, but it is just so hard for me to care enough to get involved; it mandates walking the plank into an environment dripping in hypocrisy, where highly complicated problems are reduced to black and white meme friendly soundbytes, and discussions that seem a lot more like billboards on different sides of the road than people wanting to discuss anything.   It started with the case of Hannah Poling, the little girl who experienced a dramatic and sudden developmental regression following her vaccinations at age 18 months, a case wherein the federal government conceded that vaccines through likely interaction with a pre-existing defect in mitochondrial function were likely the cause of her developmental trajectory and ‘autism like features’. 

On some parts of the Internet, you’d think that every single child with an autism diagnosis experienced a drastic, overnight regression in development that Hannah Poling did; despite abundant, clear as the day common sense evidence that the onset of autism is gradual in the overwhelming majority of instances. For the most part, I don’t think it was a spin job.  I just don’t think they get it.  Although, I must admit, I do believe that there are a very small, but real, minority of parents who have witnessed similar things with their children.  Hannah Poling is not unique. 

On the other hand, lots of other places you could find people whose online existence is part and parcel with the notion that our real autism rates are static, that the inclusion of less severe children was burgeoning our observed rates of increases, and yet, found the intellectual dishonesty to question if Hannah Poling had autism or not, as if suddenly, in this one particular instance, a diagnostic report of having ‘features of autism’ as opposed to ‘autism’ was meaningful. As if that fucking mattered.  

On the one side there is the failure to recognize any semblance of nuance, of complexity, and on the other, a startling hypocrisy and lack of curiosity.  

A few weeks ago (maybe a few months ago, by the time I finally get this post published, at my rate), a paper came out that reported, among other things, children with autism were more likely to have mitochondrial dysfunction, mtDNA overreplication, and mtDNA deletions than typically developing children.  That paper, of course, is Mitochondrial Disorder In Autism, a new winner in the field of simple to understand, straightforward titles.  The good news is that Mitochondrial Disorder In Autism is another portrait of beautiful and humbling complexity with something to offer an open mind.  Maddeningly, my real world email address received an embargo copy of the paper, which is somehow protected from copy paste operations, meaning most parts from that paper here will be manually transcribed, or more likely, paraphrased.

This is a cool paper, it sheds light on the possible participation of a widely observed phenomena in autism, increased oxidative stress, gives us additional evidence that the broader incidence of mitochondrial dysfunction is significantly very higher in the autism population, and an possible illustration of a feedback loop.

Very briefly paraphrased (damn you, embargo copy!), the authors used samples of peripheral cells of the immune system, lymphocytes, to test for mitochondrial dysfunction.  This is a big step, it allowed the researchers to bypass the traditional method of muscle biopsy, which is both invasive and painful.  It is reminiscent of using lymphoblastoid cells as proxies for neural cells in genetic expressions studies; the type of small, incremental data that can get lost in the headline, but has potentially broad applications.

In Mitochondrial Dysfunction in Autism, according to the authors, lymphocytes were considered sufficient surrogates because they are power hungry and derive a significant portion of their energy needs from oxidative phosphorylation; i.e, mitochondrial function.   It was small study, ten children with autism and ten controls; I’m not clear why such a small sample was used, perhaps the laboratory time and/or dollar requirements involved with detecting mitochondrial dysfunction, even in peripheral cells, mandated that such small numbers be used.  (?)   Perhaps funding could not be obtained for a larger study without some preliminary results, and as is mentioned several times in the text, these findings should be replicated if and when possible. 

Two types of changes to mtDNA were evaluated for, the ratio of the total number of mtDNA to nuclear DNA (i.e., ‘normal DNA’), and the presence of deletions of parts of mtDNA. These changes are a lot different than what we normally think of in genetic studies, and here’s my short story (barely longer than my understanding) of how.  

Each mitochondria has a variable number of mtDNA copies, usually estimated at between 2 and 10.  The understanding on what a relatively higher, or lower number of copies of mtDNA means for an organism is ongoing and nascent; for example, findings of associations with lower mtDNA levels in elderly women and cognitive decline, or finding that mtDNA copy number associate positively with fertility, both of which were published in 2010 (there are, conservatively, a brazillion other studies with a broad range of topics).  Highly salient for our purposes, however, are findings cited by this article, Oxidative Stress-related Alteration of the Copy Number of Mitochondrial DNA in Human Leukocytes, which reports that cells experiencing oxidative stress had increased number of mtDNA copies.  In Mitochonddrial Dysfunction in Autism the authors report an increase in the number of mtDNA copies in the autism group. 

Secondarily, the authors also looked for differences in mtDNA structure, but again in this instance, not in the way that we frequently think about genetic studies; they were not looking for an A replaced G mutation that exists in every gene, in every cell, in the individual, but rather, different structural components that were indicative of damage within the copies of mtDNA.  Thus, it wasn’t so much a case of a blueprint gone wrong, as much of case by case differences in mtDNA; potentially the result of exposure to reactive oxygen species during replication. 

Changes in both copy number of mtDNA (increased), and structure (mostly deletions) were observed in the autism group. 

Up and above changes to mtDNA, several biomarkers of direct and indirect mitochondrial dysfunction were measured, including lactacte to pyruvate ratios, (which have been observed abnormal previously in autism and speculated to be resultant from mitochondrial problems), mitochondrial consumption of oxygen, and hydrogen peroxide production, a known signal for some types of mitochondrial dysfunction.  Several of the biomarker findings were indicative of problems in mitochondrial function in the autism group, including impaired oxygen consumption, increased hydrogen peroxide production, and as noted by other researchers, higher pyruvate levels, with a consequent decreased lactate to pyruvate ratio compared to controls. 

These findings were described by the authors like this:

Thus, lymphocytic mitochondria in autism not only had a lower oxidative phosphorylation capacity, but also contributed to the overall increased cellular oxidative stress.

In plainer English, not only was the ability to produce energy reduced, but the propensity to create damaging byproducts, i.e., oxidative stress, i.e., ROS was increased.  Talk about a double whammy!  There have been a lot of studies of increased oxidative stress in the autism population, one of the first was Oxidative stress in autism: increased lipid peroxidation and reduced serum levels of ceruloplasmin and transferrin–the antioxidant proteins, with other titles including, Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism, Oxidative stress in autism, Brain Region-Specific Changes in Oxidative Stress and Neurotrophin Levels in Autism Spectrum Disorders (ASD) and many, many others.  Could mitochondrial dysfunction be the cause of increased oxidative stress in autism?  Could oxidative stress by the cause of mitochondrial dysfunction in autism?  Could both be occurring?

Oxidative stress deserves a free standing post (or a few), but at a high level refers to the creation of damaging particles, called reactive oxygen species by our bodies during the course of many biological operations; including generating energy (i.e., the function of mitochondria).  The graceful management of these particles is essential for normal functioning; too little containment and there can be damage to cellular structures like cell membranes, or DNA.  You can measure these types of damage, and a wide swath of studies in the autism realm have found that on average, children with autism exhibit a state of increased oxidative stress when compared to children without that diagnosis.  A great variety of conditions other than autism, but which you’d still generally rather not have, are also characterized by increased oxidative stress, as are things that you can’t really help having, like getting old. 

(It should be noted, however, that in an illustration of humbling complexity, we are now learning that containing free radicals by all means possible may also not necessarily be a good idea; our bodies utilize these chemicals as signals for a variety of things that aren’t immediately obvious.  For example, there is preliminary evidence that too much antioxidants can cancel out, the benefits of exercise; our bodies were using the effects of exercise as a signal to build more muscle, likewise, we have evidence that oxidative stress plays a part in apotosis, or programmed cell death, and interfering with that may not be a good idea; in fact, it could, participate in carcinogenisis.  There is no free lunch.)

Mitochondrial Dysfunction in Autism speculates that oxidative stress and mitochondrial dysfunction could be linked, either by increased oxidative stress leading to problems in mtDNA replication (i.e., the observed mtDNA problems are a result of aggressive attempts at repair, repair to damage induced by the presence of reactive species), or by deficiencies in the ability to remove ROS; i.e., decreased glutathione levels as observed by James.   This really speaks towards the possibility of a feedback loop, something leads to an increase in oxidative stress that cannot be successfully managed, which causes mitochondrial damage, which leads to problems in mtDNA replication, which in turn, leads to dysfunction, and increased oxidative stress.  Again, from the paper:

Differences in mtDNA parameters between control children and those with autism could stem from either higher oxidative stress or inadequate removal of these harmful species. The increased reactive oxygen species production observed in this exploratory study is consistent with the higher ratio of oxidized NADH to reduced glutathione in lymphoblastoid cells and mitochondria from children with ASD, supporting the concept that these cells from children with autism present higher oxidative stress.  Increased reactive oxygen species production induced by mitochondrial dysfunction could elicit chronic oxidative stress that enhances mtDNA replication and possibly mtDNA repair.

Collectively, these results suggest that cumulative damage and oxidative stress over time may (through reduced capacity to generate functional mitochondria) influence the onset or severity of autism and its comorbid symptoms.

 

 
 

 

(My emphasis).  More on why a little later.

There is a lengthy section of the paper regarding the limitations of the study, including a relatively small sample set, racial differences between the participants, and the possibility that the number of evaluations made could impact the strength of some associations.  Detangling the arrow of causality is not possible from this paper, and likely involves different pathways in different patients.  None the less, it is additional confirmation of something gone awry in the power processing centers of cells in people with autism.  

This is a pretty small study, from a number of subjects perspective, and the pilot nature of the study is somewhat of a problem in trying to determine how much caution we must use when attempting to generalize the findings to a larger population.  However, on the other hand, if we look towards earlier findings, some of which were linked above, the reports in Giulivi should not really be that surprising. In fact, we should have been amazed if they hadn’t observed mitochondrial problems. 

Here is why:

We have voluminous observations of a state of increased oxidative stress in the autism population; Chauhan 2004, Zoroglu 2004, James 2004, Ming 2005, Yao 2006, James 2009, Sajdel-Sulkowska 2009, Al-Mosalem 2009, De Felice 2009, Krajcovicová-Kudlácková M 2009, El-Ansari 2010, Mostafa 2010, Youn 2010, Meguid 2010, and Sajdel-Sulkowska 2010, all are clinical trials that reported either increased levels of oxidative stress markers, decreased levels of detoxification markers, or both, in the autism group.  There is no way, absolutely no way that children with autism have less oxidative stress, or the same oxidative stress than children without that diagnosis, barring some mechanism by which all of the above studies are wrong in exactly the same direction.  There is just too much evidence to support an association, and as far as I know, (?) no evidence to counter balance that association.  [Please note that the above studies are for biomarker based studies only, I left out several genetic studies with similar end game conclusions; i.e., alleles known to be associated with increased oxidative stress and/or mitochondrial function are also associated with an autism diagnosis.]

We also have just a large body of clinical evidence that tells us that as oxidative stress and mitochondrial function are closely linked, as oxidative stress increases, so too do problems with mitochondrial function and/or replication; Richter 1998, Beckman 1998, Lu 1999Lee 2000, Wei 2001, Lee 2002,  Liu 2003, Liu 2005, Min Shen 2008 are useful examples.  Unless all of these studies, and many more, are incorrect in the same way, and the underlying physical foundations of why oxidative stress would lead to mitochondrial function are also incorrect, we must conclude that a state of increased oxidative stress, as observed repeatedly in autism, leads to a degradation of mitochondrial function. 

It turns out, there also a growing body of evidence linking oxidative stress and/or mitochondrial dysfunction to other conditions with a neurological basis (Rezin 2009), such as schizophrenia, (Prabakaran 2004, Wood, 2009, Martins-de-Souza 2010, Verge 2010Bitanihirwe 2011) or bi-polar disorder (Andreazza 2010, Clay 2010, Kato 2006, Kaikuchi 2005).  Here is the abstract for Oxidative stress in psychiatric disorders: evidence base and therapeutic implications:

Oxidative stress has been implicated in the pathogenesis of diverse disease states, and may be a common pathogenic mechanism underlying many major psychiatric disorders, as the brain has comparatively greater vulnerability to oxidative damage. This review aims to examine the current evidence for the role of oxidative stress in psychiatric disorders, and its academic and clinical implications. A literature search was conducted using the Medline, Pubmed, PsycINFO, CINAHL PLUS, BIOSIS Preview, and Cochrane databases, with a time-frame extending to September 2007. The broadest data for oxidative stress mechanisms have been derived from studies conducted in schizophrenia, where evidence is available from different areas of oxidative research, including oxidative marker assays, psychopharmacology studies, and clinical trials of antioxidants. For bipolar disorder and depression, a solid foundation for oxidative stress hypotheses has been provided by biochemical, genetic, pharmacological, preclinical therapeutic studies and one clinical trial. Oxidative pathophysiology in anxiety disorders is strongly supported by animal models, and also by human biochemical data. Pilot studies have suggested efficacy of N-acetylcysteine in cocaine dependence, while early evidence is accumulating for oxidative mechanisms in autism and attention deficit hyperactivity disorder. In conclusion, multi-dimensional data support the role of oxidative stress in diverse psychiatric disorders. These data not only suggest that oxidative mechanisms may form unifying common pathogenic pathways in psychiatric disorders, but also introduce new targets for the development of therapeutic interventions.

(my emphasis)

Given all of this, one might consider casting an extremely skeptical eye towards the argument that the observations in Mitochondrial Dysfunction in Autism are insufficiently powered to reach any conclusions about an association; at this point, I think it is fair to say that what should have been surprising finding would have been a lack of mitochondrial dysfunction in autism.   We need to rethink some foundational ideas about the relationship between oxidative stress, mitochondrial function, other neurological disorders, and/or assume that a dozen studies are all incorrect in the same way before the small number of participants and other limitations of this study should cause us to cast too much doubt on the findings.  The findings in Mitochondrial Dysfunction in Autism are not due to random chance.

All that being said, there are still lots of questions; the most intriguing ones I’ve seen raised in other discussions on this paper would include, Is the mitochondrial dysfunction physiologically significant? and secondly, What has caused so many children with autism to exhibit these physiological differences? 

I’ll admit it, early on in my online/autism persona lifetime, I’d have viewed the first question as largely deserving of a healthy dose of (hilariously delivered) sarcasm.  But the reality is that this is a more difficult question to answer than it would seem on the surface.  The reasons I’ve seen posited that this might be valid sound pretty good at first glance, i.e., the brain is the most prolific user of energy in the body, and problem with energy creation there are pretty simple to equate to cognitive problems.   And this might be what is happening, I don’t believe we have enough information reach any conclusions.  I will note, however, with no small amount of amusement, that the online ‘skeptical’ community had no problem with this exact argument in discussing what happened to Hannah Poling, as long as it was exceptionally rare. 

Specifically speaking towards the problems of physiological significance, we haven’t any direct evidence one way or the other that the mitochondrial dysfunction observed in muscle biopsy or lymphocytes is present in the CNS of people with autism, and this is an important distinction; it is known that there are large differences in mitochondrial need and function between tissue type, and it is almost always dangerous to assume that because you see something outside the privileges of the blood brain barrier, that you will see the same thing within it.  Therefore, we should remember that it is possible that the brains are unaffected, while the peripheral cells are.   

However, we do have some indirect evidence to suggest that there are mitochondrial function problems in the CNS in the autism population.  Based on studies that have measured oxidative stress levels in the brain, specifically Brain Region-Specific Changes in Oxidative Stress and Neurotrophin Levels in Autism Spectrum Disorders (ASD) we have preliminary evidence that areas of the brain are affected by high levels of oxidative stress.  Furthermore, we have a multitude of studies regarding an ongoing immune response in the brain in autism, and we know that the immune response can generate oxidative stress, and indeed, interact with some of the results of oxidative stress, potentially participating in a feedback loop.  

In short, we know that inflammation, oxidative stress, and mitochondrial function are closely linked; considering the fact that we have evidence of two of these processes being altered in the CNS in autism, barring an unforeseen mechanism by which this association is not in place in the brain, an exceedingly unlikely situation given our observations in other cognitive domains, it seems probable that some degree of mitochondrial dysfunction occurs in the brain as well as the periphery.   If this is sufficient to cause autism will require more studies; some evaluations correlating behavioral severity and / or multiple evaluations over time would be good starting points. as well, of course, as direct CNS evaluation.

The second question, towards relevance of these findings, the reason such a large percentage of children with autism appear to have characteristics of mitochondrial dysfunction is even more difficult to detangle.  The potential of a feedback loop existing between oxidative stress and mitochondrial function was problematic enough, but it seems likely there could be other participants, for example, the immune system.  There are repeated observations of an exaggerated immune response, from genetic predispositions to known toll like receptor promoters, circulating levels of endogenous factors associated with a vigorous immune response, baseline levels of cytokines and chemokines, and cytokine values resulting from direct toll like receptor activation.  Is the over active inflammatory response observed in autism causing the mitochondrial dysfunction through an increase in oxidative stress?  Is the increased oxidative stress causing an ongoing inflammatory response?  Studies evaluating for a relationship between these parameters would help to answer these questions.

For a real world example of why such a relationship might be possible, we can take a look at a paper that landed in my inbox around the same time that Mitochondrial Dysfunction in Autism did, Dopaminergic neuronal injury in the adult rat brain following neonatal exposure to lipopolysaccharide and the silent neurotoxicity.  This paper is another that shows some very difficult to predict outcomes as a response to an early life immune challenge.  Here is the abstract:

Our previous studies have shown that neonatal exposure to lipopolysaccharide (LPS) resulted in motor dysfunction and dopaminergic neuronal injury in the juvenile rat brain. To further examine whether neonatal LPS exposure has persisting effects in adult rats, motor behaviors were examined from postnatal day 7 (P7) to P70 and brain injury was determined in P70 rats following an intracerebral injection of LPS (1 mg/kg) in P5 Sprague–Dawley male rats. Although neonatal LPS exposure resulted in hyperactivity in locomotion and stereotyped tasks, and other disturbances of motor behaviors, the impaired motor functions were spontaneously recovered by P70. On the other hand, neonatal LPS-induced injury to the dopaminergic system such as the loss of dendrites and reduced tyrosine hydroxylase immunoreactivity in the substantia nigra persisted in P70 rats. Neonatal LPS exposure also resulted in sustained inflammatory responses in the P70 rat brain, as indicated by an increased number of activated microglia and elevation of interleukin-1b and interleukin-6 content in the rat brain. In addition, when challenged with methamphetamine (METH, 0.5 mg/kg) subcutaneously, rats with neonatal LPS exposure had significantly increased responses in METH-induced locomotion and stereotypy behaviors as compared to those without LPS exposure. These results indicate that although neonatal LPS-induced neurobehavioral impairment is spontaneously recoverable, the LPS exposure-induced persistent injury to the dopaminergic system and the chronic inflammation may represent the existence of silent neurotoxicity. Our data further suggest that the compromised dendritic mitochondrial function might contribute, at least partially, to the silent neurotoxicity.

(my emphasis)

Briefly, the researchers challenged the animals with an immune stimulator shortly after birth, and then went on to observe chronic microglial activation and inhibited mitochondrial function into adulthood.  Behavioral problems included hyperactivity and stereotyped tasks (though these behaviors appeared to reverse in adulthood.  Subsequent challenge with methamphetamine in adulthood resulted in increased locomotive and stereotyped behaviors in the treatment group. 

Check that out!  These animals never actually got sick, their immune system had only been fooled into thinking that it was under pathogen attack, and yet, still showed chronic activation of the neuroimmune system and impaired mitochondrial function in dendrites into adulthood!  ).  In a sense, it might be appropriate to say, then, that the behaviors were not a state of stasis.  Talk about an inconvenient finding.

There is also the possibility that exposure to chemicals, such as pesticides, may be able to cause mitochondrial dysfunction. 

Finally, during the time it took me to put this post together, several other reviews of Mitochondrial Dysfunction in Autism landed online in places that purport to be bound by objective and dispassionate evaluation of the science of autism; Respectful Insolencence, LBRB, and Science2.0 all had posts (probably others too).  [The masochists out there that go through the discussion threads will note that several of the thoughts in this posting were experimented with in responses to these threads, ideas which were largely, or entirely, ignored.]  If you were to read these other reviews (I would recommend that you do), you might come away with the impression that Mitochondrial Dysfunction in Autism consisted of nothing more than criteria for selecting participants and limitations of the study.  The calls for caution in running wild with these findings are there, and I largely agree with this sense of caution, as is the admission that this is an area that should be studied more intently, but nowhere was there any acknowledgement of the consistency between these findings and the repeated observations of increased oxidative stress in autism and the biological reality that oxidative stress is linked with mitochondria function, nowhere was there any mention of the fact that the findings were in alignment with deficiencies in detoxification pathways as observed multiple times in autism, nowhere was there anything regarding our voluminous evidence of impaired mitochondrial function in a veritable spectrum of cognitive disorders.  Did the online skeptical community get a different copy of the paper that I did?  Perhaps, were they unaware of the repeated reports of increased oxidative stress in autism, and the incontrovertible evidence of an association between oxidative stress and mitochondrial dysfunction?  Is there a chance that their pubmed results regarding mitochondria and disorders like schizophrenia or bi-polar disorder are different than mine? 

I am afraid that this is what the vaccine wars and wrangling over the meaning of neurodiversity have done to us; the skeptical community absolutely went “all in” on the premise that the Hannah Poling concession was founded on a very, very rare biological condition.  They have sunk one hundred and ten percent of their credibility behind the notion that thimerosal based studies and MMR based studies are sufficient to answer the question of if vaccines can cause autism, or if we must, features of autism.  And now, with converging evidence from several directions pointing towards a confluence of mitochondria impairment and oxidative stress in autism and other neurological conditions, speaking towards the meat of Mitochondrial Dysfunction in Autism is more than just eating crow, it is akin to blaspheming, for if diagnosable mitochondrial disorder affects a meaningful fraction of children with autism, and mitochondrial dysfunction a  much larger percentage, the foundations behind the meme of the vaccine question as one that needs no further evaluations begins to fall apart.  That is a legitmately scary proposition, but one that is going to have to be reckoned with sooner or later; the only difference is that the more time passes, the greater the credibility strain on the mainstream medical establishment when, eventually, it is admitted, that we need to come up with good ways to generate quality information on vaccinated and unvaccinated populations. 

Similarly there is remakarble opposition in some quarters to the idea of imparied detoxificiation pathways, or indeed, a state of increased oxidative stress in some of the same places.  I think the underlying reason for this is that some of these early findings were used by some DAN doctors to promote things like chelation, almost certainly the wrong treatment for the overwhelming majority of children on whom it was performed; and in a well intentioned zeal to discount some of these practioners, as well as the outrage over statements by some (i.e., ‘toxic children’), the reality of the situation; that our children are more likely to have increased oxidative stress, do have less glutiathione,  became acceptable facts to bypass in the rush to hurl insults or wax poetic.   We can acknowlege that children with autism have these conditions while simultaneously expressing concern, or outrage, at the notion that this makes them poisonous; but ignoring the physiological reality of our findings does nothing to help anyone.  The data is the data. 

This is all too bad.  In fact, it is worse than too bad; there is no reason, absolutely no reason that a discussion on mitochondrial impairment must focus exclusively on the vaccine question, in fact, just the opposite.  There are lots of ways to achieve an endpoint of mitochondrial dysfunction, and lots of things besides vaccines that can be problematic for people with this problem. (including, of course, actual infection!)  But we have become so polarized, so reliant on hearing the same soundbyte laden diatribes, that any sense of nuance on the question immediately labels on as ‘anti vaccine’, ‘anti science’ (even worse!), or for that matter, ‘pro-vaccine’ or shill.  The questions raised by Mitochondrial Dysfunction in Autism are important and aren’t going to go away, no matter how inconvenient the follow up findings may be.  

– pD


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