Mitochondria and Autism

What causes autism?  That's the billion dollar question as the number of children who develop the condition seems to be increasing.  Autism spectrum disorders is the medical term used to represent this range of conditions characterized by impaired social interactions and communication problems.  Individuals with autism also frequently engage in repetitive and/or restrictive behaviors, for example, what such a person is willing to eat may be a very short menu indeed.

Now it looks like mitochondria, those fascinating energy machines found inside our cells, and without which we couldn't begin to be the multicellular, complex organisms we are, may have a role.  That's in this issue of JAMA.  The study took at look at an admittedly small number of children (10) aged 2 to 5 years who had a diagnosis of autism spectrum disorders.  They were matched with 10 unrelated children of the same age range without autism. 

Studies were undertaken of mitochondrial DNA and metabolism in lymphocytes collected from the subjects. Measurements of end products of metabolism were also made in the plasma.  The study found that the majority of children with autism had evidence of impaired mitochondrial function as well as DNA changes, and the authors speculate that such altered metabolism could have a very detrimental effect on the developing brain.  We know that the nervous system and specifically nerve cells known as neurons are exquisitely tuned to oxygen and glucose levels, and it stands to reason that the developing nervous system would be even more so.

Could this observation finally point the way to some concrete understanding of what goes awry in autism?  For the many thousands of parents who have had to bear the tragedy of witnessing a beloved child descend into the condition, any information is no doubt welcome.  It's a bit of a stretch from a mitrochondrial disorder to an intervention, but then who knew that looking at the behavior of tissues in a magnetic field would result in as powerful an imaging technology as MRI?

Rick and I both admit in this week's podcast to our essential nerdishness in picking this study.  Mitochondria are fascinating, since it appears that they took up residence inside other cells many millennia ago.  There they take nutrients and generate ATP, which is then used by the cell for all kinds of tasks. They also metabolize things like pyruvate, a chemical that can accumulate in exercising muscle cells, for example.

So what's in it for the mitochondria?  Presumably it's the constant flow of nutrients that makes living inside other cells so attractive.  Interestingly, in animals the DNA found inside the mitochondria originate from the organism's mother only, since sperm harbor only a very few mitochondria that are subsequently destroyed in the embryo.  This fact may account for the approximately 4:1 ratio of males to females in the development of autism, as the authors of the paper suggest.

Other topics this week include a distressing problem with dosing in over the counter medications intended for kids, also in JAMA, HIV testing in adults in Morbidity and Mortality Weekly Report, and the Institute of Medicine's new guidelines on vitamin D and calcium.  Until next week, y'all live well.

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The Huffington Post: Featuring bad science, facile reasoning since 2005
December 14, 2010 at 12:40 pm

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Discover More August 15, 2013 at 4:12 pm

Hi, excellent website you've there.

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j terry January 11, 2011 at 11:54 am

Rick I think you will find that mitochondirial DNA (mtDNA) is not a part of nuclear DNA (X or another other nuclear chromosome), but rather an unrelated circular DNA contained within the mitochondria.

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