Archive for January 2012
Extremely Long Overdue Clinical Findings “Impaired Carbohydrate Digestion and Transport and Mucosal Dysbiosis in the Intestines of Children with Autism and Gastrointestinal Disturbances”, and The Swan Song Of A Tragically Overused Autism Canard
Posted January 9, 2012on:
Hello friends –
My son was a ‘gut kid’. The irony is, for a while, because we were first time parents, we didn’t even know. My son was flagged for evaluation for autism around a year of age and we met with the autism center people several times between his first and third birthdays, with his official diagnosis coming just after he turned three. My wife came home from one of the early meetings convinced that his evaluators didn’t know the first thing about our son, autism, or anything else, and that in fact, they might be insane.
‘Do you know what those idiots asked me today?’
‘What his shits look like. My kid can’t talk and they want to ask me about his diapers!’
‘Who fucking cares?‘
We wound up caring, a lot. It turns out, this wasn’t a stupid question, it just seemed like one to us. The answer to their question was that our son was having at least four or six very messy diapers a day, his stools were never firm logs that look like they came from an spherical filter, but always, always more liquid than solid, and frequently contained chunks of identifiable food. But from our viewpoint, within the context of a child who was not speaking, hurting himself, and never looked at anyone, the idea that we should be worrying about his shit was the stupidest thing we’d ever heard.
But. When we started paying attention, starting reading, and started meeting more people with children with autism, our incredulity waned. We tried GF/CF and probiotics. We paid for lab tests to analyze the bacterial populations in his intestines. We experienced a life saving miracle with anti-fungal agents wherein my son essentially stopped hurting himself over the course of weeks after persistently banging his head dozens of times a day for six months. For nearly a year we removed all complex carbohydrates from our son’s diet, an intervention that makes GFCF feel like a Sunday afternoon after college but before kids and autism. We saw changes in our son based on how his GI tract was performing. For our son, for us, we knew that by some mechanism, what got put in his mouth, and what happened along the way was tightly coupled with how our son felt and behaved.
This is why my vision with spots of rage when I see the ideas of GI and dietary involvement with autism mocked by pseudo-skeptics so rampantly on the Internet. I cannot stand the thought of a single child continuing to suffer the way I watched my son suffer because they were told that there was no basis of GI interaction in autism. That thought hurts.
Those biases stated, we are now, finally, starting to see research indicating that in some cases of autism, there are very real, non imaginary differences in GI function.
A few months ago, Impaired Carbohydrate Digestion and Transport and Mucosal Dysbiosis in the Intestines of Children with Autism and Gastrointestinal Disturbances was published [full, dense, but very cool paper available online]. Here is the abstract.
Gastrointestinal disturbances are commonly reported in children with autism, complicate clinical management, and may contribute to behavioral impairment. Reports of deficiencies in disaccharidase enzymatic activity and of beneficial responses to probiotic and dietary therapies led us to survey gene expression and the mucoepithelial microbiota in intestinal biopsies from children with autism and gastrointestinal disease and children with gastrointestinal disease alone. Ileal transcripts encoding disaccharidases and hexose transporters were deficient in children with autism, indicating impairment of the primary pathway for carbohydrate digestion and transport in enterocytes. Deficient expression of these enzymes and transporters was associated with expression of the intestinal transcription factor, CDX2. Metagenomic analysis of intestinal bacteria revealed compositional dysbiosis manifest as decreases in Bacteroidetes, increases in the ratio of Firmicutes to Bacteroidetes, and increases in Betaproteobacteria. Expression levels of disaccharidases and transporters were associated with the abundance of affected bacterial phylotypes. These results indicate a relationship between human intestinal gene expression and bacterial community structure and may provide insights into the pathophysiology of gastrointestinal disturbances in children with autism.
I’ll admit it. From the outside, from the don’t-have-a-kid-with-autism-and-GI-problems perspective, that is some dense and seemingly bland stuff. Essentially children with GI distress and children with GI distress and autism were compared and it was found that there were distinctly qualitative differences regarding the GI function in the groups. This is validation of what a lot of us have been saying for a long time, that the GI problems our kids were experiencing weren’t coincidental to the autism, but somehow related.
For anyone who has been paying attention to the details of the autism-gut debate, these are dynamite findings. These observations are the death knell for the overused, oversimplified notion that the GI connection to autism was a function of some kids having autism, some kids having GI distress, and that therefore, some kids with autism also have GI distress. This research tells us that the reality is not so simple.
This study is the view from the microscope as opposed to the telescope, and took care not to study just anyone with an autism diagnosis, but those with an autism diagnosis and GI distress, problems so severe that invasive procedures to obtain tissue samples from the GI tract was warranted. This is a critically important facet of the study design in my opinion, a lot of the negative findings in this arena have been epidemiological, and cast the widest possible net, capturing everyone with autism and comparing them with a sample of everyone else. This is a great strength of the paper; for too long everyone has acknowledged the heterogeneous nature of autism, but few studies have tried to understand differences at a phenotype level. This paper is different.
As evidence of the non-random population, the autism patient group had a regression incidence of over eighty percent, and nearly as many of the children in both groups were reported to have food allergies.
The details of the findings in the paper get deep pretty fast, but at a high level there were differences found in proteins involved with the digestion of carbohydrates and changes in bacterial populations between the groups, with some differences found with regard to specific locations in the intestine. Based on these findings, the authors speculate that alterations in carbohydrate processing could result in abnormal bacterial populations by way of altered microbial food availability in parts of the gut.
Based on these findings, we propose a model whereby deficiencies in disaccharidases and hexose transporters alter the milieu of carbohydrates in the distal small intestine (ileum) and proximal large intestine (cecum), resulting in the supply of additional growth substrates for bacteria. These changes manifest in significant and specific compositional changes in the microbiota of AUT-GI children (see Figure 7A–C).
The authors discuss a potential feedback loop of effects of intestinal microbes and nutritional processing, and of the known and potential effects of altered bacterial populations.
Additionally, intestinal microbes can influence the expression of disaccharidases and transporters  through the influence of pathogen-associated molecular patterns (PAMPs) and butyrate (a byproduct of bacterial fermentation) on CDX2 expression and activity , , , . In this regard, the observation that CDX2 was decreased in AUT-GI children with increased levels of Betaproteobacteria may be important.
Whatever the underlying mechanisms, reduced capacity for digestion and transport of carbohydrates can have profound effects. Within the intestine, malabsorbed carbohydrates can lead to osmotic diarrhea ; non-absorbed sugars may also serve as substrates for intestinal microflora that produce fatty acids and gases (methane, hydrogen, and carbon dioxide), promoting additional GI symptoms such as bloating and flatulence .
This is very similar to the underlying theory of the Specific Carbohydrate Diet, impaired carbohydrate digestion promotes bacterial imbalances in the intestine by altered food availability, leading to gastrointestinal distress.
Because of the varied nature of the protein imbalances found and absence of the common alleles associated with such conditions, the authors report that it is unlikely that the underlying cause of the imbalances is genetically based.
In our study, 93.3% of AUT-GI children had decreased mRNA levels for at least one of the three disaccharidases (SI, MGAM, or LCT). In addition, we found decreased levels of mRNA for two important hexose transporters, SGLT1 and GLUT2. Congenital defects in these enzymes and transporters are extremely rare , , and even the common variant for adult-type hypolactasia was not responsible for reduced LCT expression in AUT-GI children in this cohort. Therefore, it is unlikely that the combined deficiency of disaccharidases (maldigestion) and transporters (malabsorption) are indicative of a primary malabsorption resulting from multiple congenital or acquired defects in each of these genes.
There are a couple of ideas presented on what might be causing the altered disaccharide transporter levels, with food composition intake, immune or hormonal irregularities, and bacterial populations and their associated fermentation byproducts listed as possible candidates. This study did not attempt to determine if any of these things were actually responsible, but an upcoming paper will also detail qualitative differences in expression of genes involved with inflammation in the autism group.
Regarding bacterial populations found, there were several differences identified by bacterial classification and location as well as some associations with onset of autistic behaviors and GI distress.
Pyrosequencing analysis of mucoepithelial bacteria revealed significant multicomponent dysbiosis in AUT-GI children, including decreased levels of Bacteroidetes, an increase in the Firmicute/Bacteroidete ratio, increased cumulative levels of Firmicutes and Proteobacteria, and increased levels of bacteria in the class Betaproteobacteria.
Stratification of AUT-GI children based on the timing of GI symptom development relative to autism onset revealed that the levels of Clostridiales and cumulative levels of Lachnospiraceae and Ruminococcaceae were significantly higher in AUT-GI children for whom GI symptoms developed before or at the same time as the onset of autism symptoms compared to AUT-GI children for whom GI symptoms developed after the onset of autism and compared to Control-GI children. However, we cannot discern whether changes in Clostridiales occurred before the onset of autism in this subgroup. We can only conclude that increased levels of Clostridiales members in biopsies taken after the development of both GI symptoms and autism are associated with the timing of GI onset relative to autism onset in this cohort. Although the reason for this association remains unclear, this finding may suggest that the timing of GI onset relative to autism is an important variable to consider in the design of future prospective studies investigating the microbiota of children with autism.
I am in love with the appreciation of the subtlety on display at the end, it may not be sufficient to simply categorize by GI and non GI autism, but also by the temporal relationship to onset of behavioral symptoms. It makes for a messy outlook going forward, but one based on pragmatism as far as coming to valid conclusions.
As is appropriate, the authors end with an admission that we are still largely groping in the dusk about how the microbiome interacts with our tightly coupled systems, but give a variety of reasons to believe that what we do know makes system wide effects reasonable and a relationship with autism plausible.
Metabolic interactions between intestinal microflora and their hosts are only beginning to be understood. Nonetheless, there is already abundant evidence that microflora can have system-wide effects , , , , , , ,  and influence immune responses, brain development and behavior , , , , .
It should be noted that this paper is a child of a 2010 IMFAR abstract, Intestinal Inflammation, Impaired Carbohydrate Metabolism and Transport, and Microbial Dysbiosis in Autism. If I understand correctly, another paper is being prepared regarding the findings of intestinal inflammation that will be complimentary to Impaired Carbohydrate Digestion and Transport and Mucosal Dysbiosis in the Intestines of Children with Autism and Gastrointestinal Disturbances. I’ll try to post something when it is published.
This study was small, with only twenty two participants, largely as a result of the difficulty in obtaining tissue specimens. While this does give us cause for caution, it is important to note that this research does not exist in a vacuum, but rather, as a much larger set of research that tell us that the relationship between GI complaints and autism is more than the inceptions of DAN doctors. Previously, Gastrointestinal abnormalities in children with autistic disorder, performed similar biochemistry and reported broadly consistent carbohydrate digestion problems, ‘Low intestinal carbohydrate digestive enzyme activity was reported in 21 children (58.3%), although there was no abnormality found in pancreatic function.’ Several other papers analyzing fecal samples have reported altered bacterial populations, including Low relative abundances of the mucolytic bacterium Akkermansia muciniphila and Bifidobacterium spp. in feces of children with autism, Gastrointestinal flora and gastrointestinal status in children with autism–comparisons to typical children and correlation with autism severity, Fecal lactoferrin and Clostridium spp. in stools of autistic children, and Pyrosequencing study of fecal microflora of autistic and control children, among others.
If the findings from this latest paper are spurious finding based on sample size problems, a lot of other studies are coincidentally finding the same type of thing in the wrong way. Does anyone think that is likely?
I entered the autism world and online autism debate from a place of seeing with my own eyes the failures of a toddlers GI function and the difficult to overstate changes in that toddler alongside improvements in his GI health. On one of the first autism blogs on which I participated I got into a discussion (argument?) with a blogger who I came to respect very much, but has since moved on. I described the fact that my son had six or more diarrhea stools, a day, every day, for months on end, and that when we added dietary changes, probiotics, and later antifungal agents, the changes to his GI function were profound and impossible to misinterpret. He told me something along the lines that humans were susceptible to illusions and sleight of hand, and I thought, ‘as if not knowing the difference between diarrhea and a log was along the lines of figuring out where the jack of spades went!’. I couldn’t believe, could not fucking believe, someone would try to convince me that I had imagined my sons problems, and associated recovery. This wasn’t a sugar pill study where I was asked if my child acted more or less hyperactive, this was a matter of asking myself, ‘How many diarrhea diapers did I change today? Six? Or Zero?’ [Repeat once a day for 180 days.]
I doubt this is necessary, but just in case, I will go on the record to state that it is easy, very easy, to tell the difference between a condition of chronic diarrhea and normal GI function. There might not be a more simpleminded determination to make on Planet Earth or indeed, our perceptible universe. This is a situation that is susceptible to placebo effects only in the most elaborate imaginations of people who have never experienced chronic GI problems.
From that time on, with nearly zero exceptions, I have become a little less shocked, but a little more saddened by the doublethink style skepticism applied to GI distress and autism in nearly every single conversation I have ever seen on the Internet. I’ve put some time thinking toward this, why so many otherwise intelligent people house such extreme hostility on a relationship between GI function and autism. I believe that the Wakefield / MMR autism debacle is at the heart of this disconnect; his ill fated and now retracted paper that launched a thousand Internet scribbles has seemingly forever tied GI complaints and autism to bad science.
It doesn’t have to be this way. As a community, the vaccine wars and kissing cousin prevalence question has done a lot to fracture us, and very little to unite us. That is a sad statement, and nothing makes it more unfortunate than the fact that it does not have to be this way. Wakefield can be wrong about the MMR and there can still be very real differences in GI function in some cases of autism. We can respectfully disagree about how well our existing prevalence studies inform us on the incidence of autism without also needing to accept a world view where every child with autism has raging bowel problems.
We should have the intellectual honesty to admit that there is nothing inherently dangerous about acknowledging what the data tells us; GI function seems to be abnormal in a subset of children with autism, and the underlying features of that GI distress are qualitatively different than what is found in ‘normal’ children.