hypothesis: common link between autism, diabetes

[Guest guest]

Common link between autism, diabetes: new study from Rice

Posted onOctober 19, 2011

<http://www.stonehearthnewsletters.com/common-link-between-autism-diabetes-new-s\

tudy-from-rice/autism/>

by Stone Hearth News <http://www.stonehearthnewsletters.com/author/admin/>

HOUSTON — (Oct. 19, 2011) — A review of the genetic and biochemical

abnormalities associated with autism reveals a possible link between the

widely diagnosed neurological disorder and Type 2 diabetes, another

medical disorder on the rise in recent decades.

“It appears that both Type 2 diabetes and autism have a common

underlying mechanism — impaired glucose tolerance and hyperinsulinemia,”

said Rice University biochemist Stern, author of the opinion

paper, which appears online in this monthÂ’s issue of Frontiers in

Cellular Endocrinology.

Hyperinsulinemia, often a precursor to insulin resistance, is a

condition characterized by excess levels of insulin in the bloodstream.

Insulin resistance is often associated with both obesity and Type 2

diabetes.

“It will be very easy for clinicians to test my hypothesis,” said Stern,

professor of biochemistry and cell biology at Rice. “They could do this

by putting autistic children on low-carbohydrate diets that minimize

insulin secretion and see if their symptoms improve.”

Stern said the new finding also suggests that glucose tolerance in

pregnant women may need to be addressed more seriously than it is now.

Stern said he first realized there could be a common link between Type 2

diabetes and autism a few years ago, but he assumed someone else had

already thought of the idea.

SternÂ’s lab, which is located at RiceÂ’s BioScience Research

Collaborative, specializes in investigating the genetic interactions

associated with genetic diseases like neurofibromatosis, a disorder in

which patients are several times more likely to be afflicted with autism

and autism spectrum disorders (ASD) like AspergerÂ’s syndrome.

Autism and ASD are neurological disorders that have a strong but poorly

understood genetic basis. The U.S. Centers for Disease Control and

Prevention estimates that about nine out of 1,000 U.S. children are

diagnosed with ASD.

Stern said at least four genes associated with increased frequency in

autism are known to produce proteins that play key roles in a

biochemical pathway known as PI3K/Tor. Stern said he had been studying a

form of abnormal function in the synapses of fruit flies that was

remarkably similar to abnormalities observed in rats and mice with

defects in a different pathway known as mGluR-mediated long-term depression.

“I had also spent a lot of time thinking about insulin signaling because

another project in my lab is an endocrinology project in which weÂ’re

studying how key proteins involved in insulin signaling affect the

timing of metamorphosis in fruit flies,” Stern said.

From his studies in both areas, Stern knew two things: PI3K/Tor was the

major pathway for insulin signals within cells, and insulin could affect

synapses in a remarkably similar way to the mGluR defects associated

with autism.

“When I read that the incidence of autism was increasing, and combined

that with the fact that the incidence of Type 2 diabetes is also

increasing, it seemed reasonable that each increase could have the same

ultimate cause — the increase in hyperinsulinemia in the general

population,” Stern said. “I didn’t do anything with this notion for a

few years because it seemed so obvious that I figured everyone already

knew this hypothesis, or had tested it and found it was not true.”

Stern said he changed his mind a few months ago when a health care

consulting firm asked him to provide input about autism.

“In preparing for this interview, I discovered that gestational diabetes

was the most important identified maternal risk factor for autism, but

that ‘no known mechanism could account for this,’” Stern recalled. “When

I read this, I was speechless. ThatÂ’s when I realized that this was not

obvious to others in the field, so I decided to write this up with the

hope that clinicians might become aware of this and treat their

patients accordingly.”

In writing the article, Stern said he learned that the role of insulin

in cognitive function is becoming more widely accepted.

“I was checking to see if insulin was known to affect synaptic function,

and I learned that the nasal application of insulin is already being

tested to see if it is beneficial for both Alzheimer’s and schizophrenia.”

Stern said he also found preliminary studies that indicated that

low-carb diets were therapeutic for some individuals with autism and ASD.

“Based on what’s already in the literature, insulin needs to be taken

seriously as a causative element in autism,” Stern said. “I hope that

clinicians will take the next step and put this to a rigorous test and

determine how to best use this information to benefit patients.”