Archive for the ‘BDNF’ Category
Considering the Scaffolds of Interconnectedness, “Environmental enrichment alters glial antigen expression and neuroimmune function in the adult rat hippocampus” and How Seeing The Obvious Can Still Be A Pleasant Surprise
Posted March 9, 2012on:
I’ve been thinking a lot lately about the beauty and trials of the tightly coupled systems, the interconnected pathways that keep popping up when pubmed tells me something that might be of interest on journey autism. One theme bubbling to the top of my thoughts is that there is a large set of inputs capable of tweaking the areas we see altered in autism; broken isn’t necessarily appropriate, but the research increasingly tells us that a delicately balanced set of connected processes is readily changed, and the way that the physics work out, there is no way to change just one thing when you have a polygamous marriage of chemical systems.
Imagine a orchestra where all of the musicians were physically bound to one or more of their counterparts, a system of wires, pulleys, springs and levers such that the musicians are actually participating in the playing of each other, not soccer players doing synchronized flips so much as a set of violin-em-cello-em robots, connected to play their instruments in unison, wind them up and create a symphony. Different orchestras might have a tighter wire from one member to another, or an older spring, but when they worked together, you could tell what composition they were playing. In this analogy, you cannot have the drummers start beating harder and faster without also changing how hard the French horn players blow. The situation only gets more complicated if some of our musicians were connected to several other musicians simultaneously. There would still be music if the cellist couldn’t keep a steady rhythm, but it would be different music, not just a different cello.
The communication between a lot of our “systems”, immune, endocrine, stress response and central nervous systems are a lot like musicians in the orchestra, interdependent and intimately connected.
The funny thing is, this same message is being blared to me, and to you, all the time, damn near every time you turn on the TV, but it is hidden in plain sight by legislatively mandated doublespeak. Consider how many advertisements each of us have seen for pharmaceutical drugs where the number of complications and contra-indicated conditions far, far exceed the number of desired effects?
Here is a list of common side effects of Viagra:
Diarrhea, dizziness, flushing, headache, heartburn, stuffy nose, upset stomach
So right off the bat, besides what we are looking for, we can see it is common to expect Viagra to also affect your GI system, immune system, and/ or brain function. These are the types of things that are “common”. (One wonders how Viagra would sell if it always caused headaches and diarrhea, and sometimes transiently ameliorated erectile dysfunction? ) A list of ‘severe’ side effects includes memory loss and a sudden decrease in hearing or vision. Even after decades of work by a lot of exceptionally smart people and hundreds of billions of dollars, the interlocked complexity of our bodies are continuing to prove very difficult to adjust in only the way we’d like, and seemingly minor perturbations in one area can pop up in very unpredictable fashion in other functions.
Trying to put my mind around the implications of this in regards to autism often leaves me with a sense of being profoundly humbled and woefully underprepared, not unlike a lot of my experiences with autism in the real world. Secondarily, again with great similarity to personal experience, I (eventually) come to the (re-)realization that we should rejoice in opportunities to be challenged and learning more about something makes us richer in ways more important than dollars.
A superb example of all of this and more landed in my inbox the other day, Environmental enrichment alters glial antigen expression and neuroimmune function in the adult rat hippocampus (Williamson et all). [Also on this paper, blog favorite, Staci Bilbo]
Williamson reported that animals given a so called ‘enriched environment’ exhibited significantly decreased immune responses in certain portions of the brain following immune challenge, with reduced levels of several chemokines and cytokines in the hippocampus in the treatment group. (A previous discussion about environmental enrichment on this blog can be found here) In this instance, the treatment group got to spend twelve hours a day in a different area, a housing unit with “a running wheel, a PVC tube and various small objects and toys”, while the control group of animals stayed in their drab, Soviet era proletariat cages all day and all night long. Here is the abstract:
Neurogenesis is a well-characterized phenomenon within the dentate gyrus (DG) of the adult hippocampus. Environmental enrichment (EE) in rodents increases neurogenesis, enhances cognition, and promotes recovery from injury. However, little is known about the effects of EE on glia (astrocytes and microglia). Given their importance in neural repair, we predicted that EE would modulate glial phenotype and/or function within the hippocampus. Adult male rats were housed either 12h/day in an enriched environment or in a standard home cage. Rats were injected with BrdU at 1week, and after 7weeks, half of the rats from each housing group were injected with lipopolysaccharide (LPS), and cytokine and chemokine expression was assessed within the periphery, hippocampus and cortex. Enriched rats had a markedly blunted pro-inflammatory response to LPS within the hippocampus. Specifically, expression of the chemokines Ccl2, Ccl3 and Cxcl2, several members of the tumor necrosis factor (TNF) family, and the pro-inflammatory cytokine IL-1ß were all significantly decreased following LPS administration in EE rats compared to controls. EE did not impact the inflammatory response to LPS in the cortex. Moreover, EE significantly increased both astrocyte (GFAP+) and microglia (Iba1+) antigen expression within the DG, but not in the CA1, CA3, or cortex. Measures of neurogenesis were not impacted by EE (BrdU and DCX staining), although hippocampal BDNF mRNA was significantly increased by EE. This study demonstrates the importance of environmental factors on the function of the immune system specifically within the brain, which can have profound effects on neural function.
Total interconnectedness kick ass!
Considering the wide ranging and predominantly ‘rather-not-have-than-have’ properties of ‘extra’ TNF-alpha and IL-1beta in the CNS, this is a pretty interesting finding. Not only that, animals ‘protected’ through environmental enrichment also showed increased levels of growth factors known to be altered in autism, again in the hippocampus. In a very real and measurable sense, it was possible to shuffle the neuroimmune cocktail of the brain by changing things like the availability of quality leisure time. As we have seen in other areas, altering the chemical milieu of immunomodulatory factors in the brain isn’t trivial, and is increasingly associated with a variety of conditions classically diagnosed through the study of behaviors.
It should be noted that there were unexpected, and generally negative findings from this study, namely, a relative lack of biomarkers indicative of increased neurogenesis in the environmental enrichment group; something that I think took the authors by a bit of surprise.
There is a short discussion on the possibilities on why the findings of differential neuroimmune responses were found only in the hippocampus, with reference being made to previous studies indicating that this area of the brain has been found to be more susceptible to a variety of insults.
There were some other findings that struck me as particularly intriguing; something that has been hinted at previously in other studies (or transcripts), but not yet well described, likely due to the fact that the area is still largely unknown to us. Specifically, the authors reported a state of glial activation, somewhat the opposite of what they expected.
The data instead suggest that EE changes the phenotype of glia, altering their activation and attenuating their pro-inflammatory response to peripheral LPS, although this remains to be directly tested. Interestingly, the blunted neuroinflammatory response within the DG of EE rats occurring concomitant with the increase in classical glial ‘‘activation’’ markers runs counter to our initial prediction. However, we believe these data simply highlight the fact that little is known about the function of these markers. Moreover, there is a growing literature that distinguishes classical versus alternative activation states in microglia, the latter of which is associated more strongly with repair (Colton, 2009; Colton and Wilcock, 2010).
Thus, it is possible that EE shifts microglia into an alternatively activated phenotype, an intriguing possibility that we are currently exploring.
The authors discuss the fact that their findings were highly spatially specific within the brain, involved a subset of cytokines and chemokines, and environmental enrichment did not seem to affect immune response in the periphery.
The immune response within the hippocampi of EE rats was markedly attenuated for a subset of cytokines and chemokines measured in our study. Importantly, not all measured immune molecules were blunted in the hippocampi of EE rats. Furthermore, the immune response was similar for each housing group in the parietal cortex as well as in the periphery. Within the hippocampus, however, EE rats had an attenuated response of interleukin-1b (IL-1b), the TNF family of genes, and several chemokines involved in the recruitment of leukocytes and monocytes. These families of genes indicate an altered hippocampal milieu in EE rats that may be less pro-inflammatory, more neuroprotective and less permeable to peripheral infiltrating immune cells.
There is a short discussion on the existing knowledge concerning IL-B and TNF-alpha in normal and pathological conditions, and how these findings are consistent with other findings involving environmental enrichment and cognition.
Tumor necrosis factor alpha (TNFa) is well characterized for its roles in inflammation and host defense, sepsis and, most intriguing for this study, apoptosis cascades (for review, see Hehlgans and Pfeffer, 2005). The observed attenuation after an immune challenge of TNFa and several associated genes in EE rats compared to HC controls indicates a potential enduring change in the hippocampal microenvironment of enriched rats, such that one mechanism by which EE may increase neuroprotection following insults to the CNS (Briones et al., 2011; Goldberg et al., 2011; Young et al., 1999) is via altered TNF tone and function, increasing the likelihood of cell survival by reducing apoptotic signaling. In addition to attenuated IL-1b and TNF responses, EE rats showed blunted responses for several chemokines known to influence the recruitment of circulating monocytes and leukocytes to the CNS.
Finally, the authors conclude how their findings add to the literature on environmental enrichment and brain function.
In summary, environmental enrichment is a relatively simple manipulation that results in robust beneficial outcomes for the brain. While previous studies have shown a role in post-insult rehabilitation for EE, our study provides evidence that enrichment need not follow the insult in order to be beneficial. Indeed, neuroinflammatory disease states might be attenuated or delayed in their onset in the face of ongoing EE. The translational reach of this manipulation remains to be explored, but in animal models of neuroinflammation, EE may provide a simple preventative measure for negative outcomes.
The bottom line is that a fuller rat life experience resulted in different neuroimmune profiles, findings with some consistency with previous observations that an enriched rat house resulted in improved behavioral manifestations of cognitive performance. The qualities of these different neuroimmune profiles are also consistent with chemical profiles associated with positive outcomes in several conditions.
There is a deceivingly startling realization hidden in these finding, startling because it reveals the malleable nature of the seemingly different, but basic systems interacting and deceptive because it is so obvious. How many of us have known someone who deteriorated upon entering a nursing home, or even retiring from working? How many of us have kept their children inside for a week due to weather and watched their children go crazy after the already inferior indoor entertainment options are long exhausted? Those changes in emotion, in behaviors and function, just like the findings from this study, are founded by chemistry.
But seeing evidence that relatively simple environmental modifications can rejigger the molecular atmosphere of the brain is still more than a little awe inspiring. Knowing there is machinery underneath the hood is a little different than observing the cogs of cognition swell , shrink, or slow down; nothing less than a deeper understanding of the chemical basis of thought. And that is pretty cool.
The Dangers Of Using Simplistic Rules To Understand Complicated Processes Or ‘The Poison Is In The Dose’ Versus Reality
Posted March 13, 2011on:
Hello friends –
There is a lot of over simplification in discussions about autism on the Internet, sometimes I don’t think the people that use them really understand that their points are founded on primitive facsimiles of reality, but other times, I’m pretty sure they do know. That second group are the ones that really leave me in a confused rage; smart enough to know better (or have had the difference explained to them previously), but continue to rely on utilization of grade school quality parameters to govern complicated and entangled systems. It seems I’m often wrong when I wonder about the reason people do things (doh!), but when someone otherwise sufficiently knowledgeable relies on the crutch of simplicity because they think it bolsters their argument, I do tend to trust their motives before I consider human fallibility. It reminds me a lot of politicians, especially Republicans. [sorry]
That being said, one of the big simplifications you used to see a lot during the thimerosal wars was this gem:
“The poison in the dose.”
I googled this a bit. This phrase is attributed to Paracelsus, who Wikipedia tells me is considered ‘the father of toxicology’. He apparently wrote this:
All things are poison, and nothing is without poison; only the dose permits something not to be poisonous.
Good stuff. By the way, Paracelsus, who no doubt was pretty smart in his day, was born over six hundred goddamn years ago and the primary observation metrics available to Paracelsus was whether or not something died or not. Sure, oxygen is deadly in sufficient concentrations, as is water, salt, and everything else, so if we want to have a discussion that allows only for endpoints of livingness or death, the parameters laid out by him are good boundaries. However, if we would like our conversations to allow for somewhat more subtle changes associated with environmental exposures, something a dispassionate evaluation of the data dictates, we may need to find ways to have conversations that allow for endpoints other than death, and we will need to acknowledge that we have lots of evidence to suggest that there are inputs other than dose that are occasionally meaningful, no matter how this might affect our ability to take comfort in one study or the other. Even worse, we have actual, real empirical data to suggest there are times when there is an inverse dose relationship.
One of my pubmed alerts somewhat tangential to autism sent me the abstract for Differential mRNA expression of neuroimmunemarkers in the hippocampus of infant mice following toluene exposure during brain developmental period. It’s a doozy:
Toluene, a volatile organic compound with a wide range of industrial applications, can exert neurotoxic and immunotoxic effects. However, the effects of toluene exposure on developmental immunotoxicity in the brain have not yet been characterized. To investigate the susceptible window to toluene exposure during development and the effects of fetal and neonatal toluene exposure on the neuroimmune markers, gestational day (GD) 14 pregnant mice, postnatal day (PND) 2 and PND 8 male offspring were exposed to filtered air (control; 0 ppm), or 5 or 50 ppm toluene for 6 h per day for five consecutive days. The neuroimmune markers in the hippocampus of PND 21 were examined using a real-time RT-PCR and immunohistochemical analysis. Mice exposed to 50 ppm toluene on PND 2–6 showed significantly increased levels of nerve growth factor (NGF) and tumor necrosis factor (TNF)- mRNAs. In contrast, NGF and brain-derived neurotrophic factor (BDNF) and proinflammatory cytokines TNF-, CCL3, NF-kB, toll-like receptor (TLR)-4, astrocyte marker glial fibrillary acidic protein (GFAP), and microglia marker ionized calcium binding adapter molecule (Iba)-1 mRNAs were increased significantly in mice exposed to 5 ppm toluene on PND 8–12. These results indicate that low-level toluene exposure during the late postnatal period (PND 8–12) might induce neuroinflammatory mediators via TLR4-dependent NF-?B pathway in the hippocampus of PND 21 male mice. Among the three developmental phases, PND 8–12 seems to be most sensitive to toluene exposure. This is the first study to show developmental phase- and dose-specific changes in neuroimmune markers in infant mice following toluene exposure.
Essentially the authors took a bunch of mice exposed them to different amounts of airborne toluene at different days before and after birth, then looked for a variety of changes in immune system markers and neurotrophic factors in the hippocampus. Toluene was certainly capable of tinkering around with lots of systems that we know are skewed in the autism population. Curiously, what they found was that there were time dependent changes that had just as much of an impact than dose of toluene; and in fact, much, much lower doses of toluene were capable of causing more robust changes if the exposure occurred during critical developmental windows.
The authors state that the timeframe of exposures in this study, postnatal days 2 -6 and postnatal days 8 – 12 roughly map to the early and late third trimester of human fetal development, respectively. I’ve seen similar equivalencies in other papers, some with earlier and later timeframes, but certainly these timeframes are generally within the range that other papers have used. Consistent with the theme of this post, I’d just say that rat to human is difficult, and rat to human specific brain area and developmental timeframe equivalency is even more difficult.
The authors speculate that the difference in effect may be related to what was happening, developmentally within the brain at the time of toluene exposure that made the impact.
During this period, hippocampus undergoes an increase in size and a change in excitatory neurotransmission to allow for adult-like synaptic plasticity by the end of the second postnatal week (Dumas, 2005). This transiently heightened level of brain plasticity is shaped byenvironmental factors which have profound effects on this brain growth spurt (Goodlett et al., 1989). Furthermore, during this period, the immune system undergoes maturation to immunocompetence (Dietert et al., 2000).
There are also some stuff about why the hippocampus is a particularly promising target for investigation into effects of toluene exposure.
Here are a couple of graphs of their findings:
Check that shit out! During some very specific developmental timeframes, a decreased exposure resulted in increased physiological effect, not only that, the more affected animals received ten times less agent. Less poison, more effect. The exact opposite of what Paracelsus predicts. [Sorry for the formatting/stupid wordpress!]
Saliently towards autism, these graphs just happen to show some measurements that have great functional overlap with findings from autism. These graphs are for CCL3, an immune bugler of sorts, a chemokine, an agent responsible for attracting components of the immune response, one numeral down for CCL2, aka MCP-1, which we’ve also seen increased in the in autism brains, iba1, a marker for microglial activation, NGF and BDNF, neurotrophic factors that have a variety of signaling and maintenance processes in the CNS, and we have much data implicating altered BDNF levels in autism.
Not only did the authors observe an inverted dose relationship, some of the measurements found that the time dependencies are also reversed from what you might expect in that later exposure was worse than earlier exposure. Environmental exposures do not necessarily follow the linear timelines you might expect.
The idea of an inverted, or skewed dose relationship has actually been explored for some time. For example, The frequency of U-shaped dose responses in the toxicological literature
Hormesis has been defined as a dose-response relationship in which there is a stimulatory response at low doses, but an inhibitory response at high doses, resulting in a U- or inverted U-shaped dose response. To assess the proportion of studies satisfying criteria for evidence of hormesis, a database was created from published toxicological literature using rigorous a priori entry and evaluative criteria. One percent (195 out of 20,285) of the published articles contained 668 dose-response relationships that met the entry criteria. Subsequent application of evaluative criteria revealed that 245 (37% of 668) dose-response relationships from 86 articles (0.4% of 20,285) satisfied requirements for evidence of hormesis. Quantitative evaluation of false-positive and false-negative responses indicated that the data were not very susceptible to such influences. A complementary analysis of all dose responses assessed by hypothesis testing or distributional analyses, where the units of comparison were treatment doses below the NOAEL, revealed that of 1089 doses below the NOAEL, 213 (19.5%) satisfied statistical significance or distributional data evaluative criteria for hormesis, 869 (80%) did not differ from the control, and 7 (0.6%) displayed evidence of false-positive values. The 32.5-fold (19.5% vs 0.6%) greater occurrence of hormetic responses than a response of similar magnitude in the opposite (negative) direction strongly supports the nonrandom nature of hormetic responses. This study, which provides the first documentation of a data-derived frequency of hormetic responses in the toxicologically oriented literature, indicates that when the study design satisfies a priori criteria (i.e., a well-defined NOAEL, > or = 2 doses below the NOAEL, and the end point measured has the capacity to display either stimulatory or inhibitory responses), hormesis is frequently encountered and is broadly represented according to agent, model, and end point. These findings have broad-based implications for study design, risk assessment methods, and the establishment of optimal drug doses and suggest important evolutionarily adaptive strategies for dose-response relationships.
We have other examples from the synthetic world that may be of interest to autism. For example, in Developmental Exposure to Polychlorinated Biphenyls Interferes with Experience-Dependent Dendritic Plasticity and Ryanodine Receptor Expression in Weanling Rats the authors report an inverted dose relationship regarding exposure to PCBs and dendrite growth.
Developmental A1254 exposure significantly enhanced dendritic growth in cerebellar Purkinje cells and neocortical pyramidal neurons among P31 rats not trained in the Morris water maze, which is consistent with our previous observations that similar exposures accelerated dendritic growth in Purkinje cells and hippocampal CA1 pyramidal neurons between P21 and P60 (Lein et al. 2007). In Purkinje cells, this effect was observed among animals in the 1 mg but not 6 mg/kg/day A1254 group, whereas in neocortical neurons, responses were comparable between A1254 groups. The reason for the different dose–response relationship in different brain regions is not known. Possibilities include regional differences in RyR regulation (Berridge 2006; De Crescenzo et al. 2006; Hertle and Yeckel 2007) or differential upregulation of cytochrome P450 enzymes by AhR ligands in the cerebellum versus neo-cortex (Iba et al. 2003), which could result in regional differences in PCB toxicodynamics and toxicokinetics, respectively.
What about situations where we have evidence for an environmental factors already associated with autism? Neuroinflammation and behavioral abnormalities after neonatal terbutaline treatment in rats: implications for autism found that terbutaline administration at postnatal day 2 -5 resulted in chronically activated microglia and behavioral abnormalities in rodents, but the same dose in days 11 – 14 resulted in no such effect. Same dose, different time, different outcome.
There is more, lots more, but how many times must a rule fail primitive logical tests before we acknowledge that it’s utility in complex discussions is extremely limited? This absolutely is not meant as an expose meant to reignite discussions about thimerosal, but rather, to illustrate the dangers of trying to understand complicated rules by leveraging simplistic heuristics. There’s a lot of that in the autism discussion landscape; it is a dangerous concoction of hubris and faith to think that we can have gain meaningful insight into our shared mystery by applying very simple rules.
I haven’t seen the ‘poison is in the dose’ canard used for a while now. Good riddance and long live models that are not exceedingly simple to invalidate.
The Beautiful, Dispassionate, and Humbling Complexity of Environmental Enrichment, Butterfly Wings, and How the Granularity of Our Filters Control What We Think We Know
Posted November 5, 2010on:
Hello friends –
I’ve been planning to write something about the idea of environmental enrichment for a while now but other stuff kept on popping up. At a broad level, researchers are finding that the type of external stimulation an animal is raised or housed in can have dizzyingly unpredictable effects on a range of physiological and behavioral endpoints, many of which are of great interest to the autism community. This is a tough area to dance through in the autism world; the available literature has shades of refrigerator mothers, and TV based causation; yet, the underlying idea of environmental enrichment, that the external environment can affect a person in a very physical way, is something known to the autism community in concrete ways. What’s more, much of our data in the environmental enrichment realm is nothing less than compelling. It is exciting to know that we are beginning to have insight into the molecular mechanisms by which the environment can affect the body and brain, and with that insight, just maybe the wisdom to help our children and help ourselves.
From the biomarker side, a couple of neat studies would include Environmental enrichment reduces Abeta levels and amyloid deposition in transgenic mice, wherein striking reductions in amyloid proteins were found in knockout mice housed in a stimulating environment compared to those in standard housing. Or the very recently published, Complex environment experience rescues impaired neurogenesis, enhances synaptic plasticity, and attenuates neuropathology in familial Alzheimer’s disease-linked APPswe/PS1DeltaE9 mice which hits a lot of keywords with parallels to the autism research world. There are many, many others including hits like Altered plasticity in hippocampal CA1, but not dentate gyrus, following long-term environmental enrichment, or hilariously named, soundbyte laden, Hippocampal epigenetic modification at the brain-derived neurotrophic factor gene induced by an enriched environment. The lower level details of these studies and their many ancestors are beyond the scope of what I have time for now, but clearly anything that can be affecting synaptic plasticity, BDNF expression, and neurogenesis should be of interest to the autism community.
If we turn to measurements that go beyond frozen slices of tissue (but do not necessary exclude them), our data regarding behavioral differences in EE housed animals is also robust. For example, we could look at Environmental enrichment delays the onset of memory deficits and reduces neuropathological hallmarks in a mouse model of Alzheimer-like neurodegeneration, which found that EE housed mice performed significantly better at memory tasks that other mice housed in non stimulatory environments. Environmental-enrichment-related variations in behavioral, biochemical, and physiologic responses of sprague-dawley and long evans rats concludes by saying, The data support the claim that environmental enrichment may render animals more resilient to challenges. Ouch. Forgetting chronic diseases such as Alzheimer’s or Parkinson’s, which get a lot of attention in the EE world, even things like traumatic brain injury or lack of oxygen to the brain seem to show benefits from a stimulating environment, as we can see from studies like Environmental Enrichment Influences BDNF and NR1 Levels in the Hippocampus and Restores Cognitive Impairment in Chronic Cerebral Hypoperfused Rats or Empirical comparison of typical and atypical environmental enrichment paradigms on functional and histological outcome after experimental traumatic brain injury. The flip side, a ‘de-enriched’ environment has findings along the lines of what you might expect; i.e., Environmental impoverishment and aging alter object recognition, spatial learning, and dentate gyrus astrocytes. Ouch.
So what is, exactly, an enriched environment? The methods section from Environmental enrichment reduces Abeta levels and amyloid deposition in transgenic mice says this:
Animal experiments were conducted in accordance with institutional and NIH guidelines. Male offspring of transgenic breeding pairs APPswe × PS1 were separated from their mother at 3 weeks of age (after weaning), genotyped, and housed four males to a cage. Enriched environment was composed of large cages running wheels, colored tunnels, toys, and chewable material. For 1 month, mice were exposed to enriched environment every day for 3 hr and were returned to their original cages for the remaining 21 hr. After 1 month of daily enrichment, mice were introduced to the enriched environment three times a week for an additional 4 months. Mice were sacrificed at age of 6months. Following weaning, a control group of animals was maintained for 5 months in standard housing conditions.
Lets consider the implications of these findings. Reducing amyloid buildup has been a holy grail of the pharmaceutical companies for a long time now, though it is possible that this plan of attack was based on bad assumptions. Tens of millions of dollars (or hundreds of millions) have been thrown at synthetic ways to reduce or eliminate the buildup of amyloid plaque in mice, rats, and recently, people with mixed to poor results. Even if it turns out that amyloid isn’t causing Alzheimer’s, that doesn’t do anything to change the fact that these researchers were able to make very significant changes to biological systems by setting their rats up in a rat mansion with rat delivered food and a rat tennis court for a few hours a day. Despite the mixed findings as of late on the effect of brain training in order to stave off dementia, I think most of us have known someone, or Kevin Baconed one degree out to know someone who has seemingly either degenerated with a stagnant environment, or kept on trucking through old age with a more active lifestyle. Is their environment participating?
So what about autism? The most extreme and tragic parallels can be seen in studies of children from orphanages, notably in Romania, where children were raised in absolutely destitute surroundings. A recent study is entitled Stereotypies in children with a history of early institutional care with these findings:
RESULTS: At the baseline assessment prior to placement in foster care (average age of 22 months), more than 60% of children in institutional care exhibited stereotypies. Follow-up assessments at 30 months, 42 months, and 54 months indicated that being placed in families significantly reduced stereotypies, and with earlier and longer placements, reductions became larger. For children in the foster care group, but not in the care as usual group, stereotypies were significantly associated with lower outcomes on measures of language and cognition.
CONCLUSIONS: Stereotypies are prevalent in children with a history of institutional care. A foster care intervention appears to have a beneficial/moderating role on reducing stereotypies, underscoring the need for early placement in home-based care for abandoned children. Children who continue to exhibit stereotypies after foster care placement are significantly more impaired on outcomes of language and cognition than children without stereotypies and thus may be a target for further assessments or interventions.
Another study that looks specifically towards autistic like behaviors in children raised in orphanages is Early adolescent outcomes of institutionally deprived and non-deprived adoptees. III. Quasi-autism.
BACKGROUND: Some young children reared in profoundly depriving institutions have been found to show autistic-like patterns, but the developmental significance of these features is unknown.
METHODS: A randomly selected, age-stratified, sample of 144 children who had experienced an institutional upbringing in Romania and who were adopted by UK families was studied at 4, 6, and 11 years, and compared with a non-institutionalised sample of 52 domestic adoptees. Twenty-eight children, all from Romanian institutions, for whom the possibility of quasi-autism had been raised, were assessed using the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) at the age of 12 years.
RESULTS: Sixteen children were found to have a quasi-autistic pattern; a rate of 9.2% in the Romanian institution-reared adoptees with an IQ of at least 50 as compared with 0% in the domestic adoptees. There were a further 12 children with some autistic-like features, but for whom the quasi-autism designation was not confirmed. The follow-up of the children showed that a quarter of the children lost their autistic-like features by 11. Disinhibited attachment and poor peer relationships were also present in over half of the children with quasi-autism.
CONCLUSIONS: The findings at age 11/12 years confirmed the reality and clinical significance of the quasi-autistic patterns seen in over 1 in 10 of the children who experienced profound institutional deprivation. Although there were important similarities with ‘ordinary’ autism, the dissimilarities suggest a different meaning.
Similarly depressing findings can be found in places like Institutional rearing and psychiatric disorders in Romanian preschool children, or Placement in foster care enhances quality of attachment among young institutionalized children. There is a gripping This American Life about a child adopted from Romania. Please be sure your head is in the right place before listening to part II, which describes a family trying to decide of their very severely autistic son should be placed in residential care. I ran into this episode on accident one day in the car when I was already feeling bleak and walked out the other end pretty fucked up for a few days; those guys are really good and the narrative can hit very close to home for some.
Calling up images from the dark(er) days of autism and Bettleheim we have an array of studies on the effect of maternal separation and subsequent physiological and behavioral effects that have parallels in autism findings. For example, here is an abstract from Behavioural and neurochemical consequences of early weaning in rodents
Among all mammalian species, pups are highly dependent on their mother not only for nutrition, but also for physical interaction. Therefore, disruption of the mother-pup interaction changes the physiology and behaviour of pups. We review how maternal separation in the early developmental period brings about changes in the behaviour and neuronal systems of the offspring of rats and mice. Early weaning in mice results in adulthood a persistent increase in anxiety-like and aggressive behaviour. The early-weaned mice also show higher hypothalamic-pituitary-adrenal activity in response to novelty stress. Neurochemically, the early-weaned male mice, but not female mice, show precocious myelination in the amygdala, decreased brain-derived neurotrophic factor protein levels in the hippocampus and prefrontal cortex, and reduced bromodeoxyuridine immunoreactivity in the dentate gyrus. Because higher corticosterone levels are persistently observed up to 48 h when the mice are weaned on postnatal day 14, the exposure of the developing brain to higher corticosterone levels may be one of the effects of early weaning. These results suggest that deprivation of the mother-infant interaction during the late lactating period results in behavioural and neurochemical changes in adulthood and that these stress responses are sexually dimorphic (i.e. the male is more vulnerable to early weaning stress).
The rapidfire analysis tells us that altered HPA-Axis activity, BDNF levels, and anxiety all have parallels in autism, along with perhaps the most consistent finding in animal studies that have interest to autism, the problems of being born male and consequent risk factors from nearly everything. This is a review paper, but there are a gazillion others with titles like Maternal separation disrupts dendritic morphology of neurons in prefrontal cortex, hippocampus, and nucleus accumbens in male rat offspring, Short- and long-term consequences of different early environmental conditions on central immunoreactive oxytocin and arginine vasopressin levels in male rats, or Prolonged maternal separation decreases granule cell number in the dentate gyrus of 3-week-old male rats.
Though I’m pretty sure that this should be clear to everyone, just to be sure, I’m not proposing a refrigerator mother theory of autism. But the data is the data and the logical opposite of an enriched environment is also born out.
So what? Well, this reminded me of the “Rat Park” studies an Internet friend told me about, wherein researchers seemed to find that animals dosed with opiates for several weeks would voluntarily wean themselves from the drugs if moved to much larger enclosures where they had access to either drugged water or plain water. The startling thing about the Rat Park studies isn’t so much what was learned about opiate addiction, so much as the broader implications that the existing studies on drug addiction might not be studying the right thing; that instead of testing the effects on opiate availability on rodents, they were testing the effects of opiate availability on chronically depressed rodents. Following through, it occurs to me that in addition to the bazillion other problems we have moving from rodent to human with anything other than a hopeful educated guess, we must grudgingly admit that the condition the animals were housed in may be affecting a lot of findings. As if we didn’t have enough confounders already!
But more importantly, these types of findings are beautiful portraits of complexity, the dispassionate hand of nature and the dangers of thinking you understand.
There are so many instances where we have found that as we gain the ability to make more detailed observations, we learn that our existing conclusions were crude facsimiles of reality, and oftentimes, conclusions that had been formed on dangerously unsound foundations. By way of example, exposure to lead and consequent effects on neurodevelopment. At one point, lead was used as a pesticide, eventually we figured out that wasn’t such a good idea, but it should be fine in paint and gasoline. Then we removed it from paint. Then gasoline. And just a few years back, the ‘safe’ level of lead was deemed to be zero; and even the tiniest increases in lead were associated with developmental problems. Of course, this was always the reality, but it was not until we applied filters of sufficient sophistication that our observations were adequately powered to understand the reality. Are our studies of any number of factors clever enough to discern the changes we’d like to understand when we realize that subtle changes are still changes?
It gets thornier for the autism community in particular. One thing a lot of our kids aren’t very good at are “complex environmental interactions”, in fact, a lot of our kids are flat out terrible at them. After a couple of weeks/months/years of soul crushing experiences trying new things out with kid autism, some parents might start to think to themselves that a trip to the zoo, or the museum, or the movie theater or even the super market just isn’t worth it. The result, while not necessarily an abject environment can start to resemble a single square mile of ocean, indistinguishable from the sea for backwards or forwards; the real world equivalent of a DVD set on repeat play. I speak from experience, a rule in our household when one of the parents had to leave the other home for a weekend with kid autism was ‘survive, don’t thrive’. If that meant a trip to the same lake, spinning the same DVD, and a meal of the same food, but a relatively meltdown free weekend, that was OK.
We survived, but did we spite ourselves in the process? Were we reinforcing at a neurochemical level some of the causes of the very behaviors that were causing us to retreat to the middle of the ocean? We are starting to learn that this might be somewhat of a self fulfilling prophecy; taking a child who already does very poorly in new environments and run him or her through the same things over and over could be exacerbating their ability to handle new environments in a physiological way. The data is the data.
That being said, there is an upside, a big one; the flip side is that parents have a chance to make real and salient changes in their child by the least controversial methods possible; gentle but repeated exposure to new things. For some of us, this means a lot of shitty days and late night drinks to get through to the other side. That’s OK. It’s worth it. Steel yourself for a meltdown and turn off the goddamned TV, take kid autism to the zoo, or the bounce house playground, or art festival, or a ‘non-autism’ friends house. A lot of our children might need a helping hand, a gentle push, or a well meaning shove into the world, but someone has to do it, and the world isn’t going to get any less complicated while we wait. When it works out, and you have even a single new experience your child enjoys, that is an enriched environment for you, and enriched environments aren’t just for rats and kids.
Hello friends –
I ran into a few abstracts, read a few papers, and tried to get my way through one really dense paper in the past few weeks that got me thinking about this post. It’s all shook up, like pasta primavera in my head, but hopefully something cogent will come out the other end. (?)
Of the metabolic conditions known to be associated with having a child with autism, hypothyroidism is one that I keep on running into by way of the pubmed alert grapevine. By way of example, we have two studies that looked for autoimmune conditions in family members which found hypothyroidism to be one of many autoimmune diseases as a risk factor for autism, including, Familial clustering of autoimmune disorders and evaluation of medical risk factors in autism, and Increased prevalence of familial autoimmunity in probands with pervasive developmental disorders. This shouldn’t be too surprising, we know that, for example, perinatal hypothyroidism is a leading cause of mental retardation, with similar findings for the condition during pregnancy. It turns out, it appears that rates of hypothyroidism are slightly increasing, though at this time, the increases are of relatively small proportions, and as such, may be artifacts unrelated to an actual increase in classically recognized hypothyroidism. In any case, I think it is safe to say that interference with thyroid metabolism is something to be avoided at all costs when possible.
So after having read about that, this paper showed up in my inbox a while ago:
Thyroid hormones have long been known to play important roles in the development and functions of the central nervous system, however, the precise molecular mechanisms that regulate thyroid hormone-responsive gene expression are not well understood. The present study investigated the role of DNA methylaion and histone acetylation in the effects of perinatal hypothyroidism on regulation of reelin and brain-derived neurotrophic factor (BDNF) gene expression in rat hippocampus. The findings indicated that the activities of DNA methyltransferase (DNMT), methylated reelin and BDNF genes were up-regulated, whereas, the activities of histone acetylases (HAT), the levels of global acetylated histone 3 (H3) and global acetylated histone 4 (H4), and acetylated H3, acetylated H4 at reelin promoter and at BDNF gene promoter for exon II were down-regulated in the hippocampus at the developmental stage of the hypothyroid animals. These results suggest that epigenetic modification of chromatin might underlie the mechanisms of hypothyroidism-induced down-regulation of reelin and BDNF gene expression in developmental rat hippocampus
This gets interesting for autism because reelin, and bdnf levels have been found to be decreased in several studies in the autism population, with direct measurements, genetic expression, mouse knockout based models of autism , and genomic alterations all being implicated. There have been some negative genetic studies, but considering that it isn’t always the genes you have, but the genes you use, our other available evidence certainly points to BDNF and reelin involvement with some percentage of children with autism, and the association is such that a reduction in reelin or BDNF is a risk factor for developing autism. It would seem that the paper above might give some insight into the lower level details of the effects of hypothyroidism and subsequent developmental trajectories; modifications of reelin expression; through epigentic mechanisms, no less!. That’s pretty cool!
Then, I got my hands on a review paper that tries to go into detail as to the functional mechanism by which reelin deficiency could contribute to ASD, Neuroendocrine pathways altered in autism. Special role of reelin. It is a review that touches on a variety of ways that reelin contributes to neurodevelopment that have findings in the autism realm, including neuronal targeting and migration during brain formation, interactions with the serotonin and GABA systems, testosterone, and oxytocin. In short, there are plenty of ways that decreased reelin expression can impact development in ways that mirror our some of our observations in autism.
Of the many things that convince me that we are doomed, the proliferation of chemical compounds whose interactions within our bodies we scarcely understand is among them. In my readings on endocrine disruptors, one thing I found that seemed to be worrying lots of researchers was that some classes of these chemicals are capable of interfering with thyroid metabolism, and in some cases interfering with development of cells known to be associated with autism. Terrifyingly enough, since I read those papers, several others have come out, including Polybrominated Diphenylether (PBDE) Flame Retardants and Thyroid Hormone during Pregnancy and Mini-review: polybrominated diphenyl ether (PBDE) flame retardants as potential autism risk factors. At this point, it is important to point out that, as far as I know, there have not been any studies showing that non occupational exposure to PDBEs or other environmental pollutants can lead to classically defined hypothyroidism, at least none that I know of. (?) Be that as it may, I think it is realistic to assume any interference in thyroid metabolism is a bad thing, and while finding people in the outlier regions of hypo (or hyper) thyroidism gives us information on extreme environments, it would take someone with a lot of misplaced faith to assume that we can safely disturb thyroid metabolism just a little bit, and everything will come out in the wash.
I’ve had the argument made to me in the past that environmental pollutant driven increases in autism lacked biological plausible mechanisms; this argument is almost always made within a context of trying to defend the concept of a static rate of autism. While the papers I’ve linked to above do not provide conclusive proof that our changing environment is causing more children to be born with autism, they do provide increasing evidence of a pathway from pollutants to ASD, and indeed, the lack of biological plausibility becomes an increasingly flacid foundation on which to assume that our observations of an increased rate of autism are illusory. Unfortunately, in my opinion, the focus on vaccines has contributed to the mindset that a static rate of autism (or nowadays, maybe a tiny increase), must be protected at all costs, including some ideas on the application of a precautionary principle that seem outright insane to me (or at least, the exact opposite of what I would consider to be a precautionary path).
One thing is for certain, the number of child bearing women in developing countries with measurable concentrations of chemicals known to interferre with thyroid metabolism nears 100% in the industrialized nation as we eat , drink, breathe and bathe in the microscopic remnants of packaging materials, deteriorating carpet fibers, and baby clothes that are made to be fire resistant. This is an environment unambiguously different than that encountered by any other generation of infants in the history of mankind. To believe that we can modify our environment so drastically without having an impact seems incredibly naive to me, or on some days, just plain old stupid.