Anyone not up to date on the wide-ranging microbiome discussion is invited to catch up by revisiting “Connecting the Universe of Dots” and “The Microbiome — More Dots to Connect.” The photo on this page is a reminder of how the ancients sought patterns in the skyful of stars.
The basic theory of the microbiome is, the bacteria that make their home inside of us probably do a lot more than is suspected by even their most enthusiastic proponents. We have been looking at their relationship to allergies and addiction. What other kinds of mischief can the gut bacteria get up to?
The neurodevelopmental problem known as Autism Spectrum Disorder resides in the brain and/or central nervous system, yet somehow also influences body size and weight. A typical reference says:
The investigators also found lesser but significant increases in obesity rates among teens with autism and among children whose autism was complicated by sleep and mood problems, the latter including depression and anxiety.
A while back, we mentioned an article from the journal Pediatrics that spoke of a link between obesity and autism, and a report in Current Biology that drew lines between previously isolated dots. Obesity and autism are connected. Autism and the neurotransmitter GABA are connected. GABA has a close relationship with at least two kinds of gut bacteria, Flavonifractor sp. and Bacteroides fragilis, that seem to be linked somehow to autism.
And then, there is Clostridia. An essay from Economist.com reminds us that the link between autism and intestinal problems has long been recognized. Investigation has shown that the microbiomes of people afflicted with autism contain large populations of this organism. No one has proven that Clostridia actually causes autism, but the link is definitely present. In its effort to kill off competing bacteria, Clostridia produces phenols, which are poisonous to human cells.
So the body neutralizes phenols with sulphate. Interestingly, a lot of autistic people have a genetic defect that prevents them from metabolizing sulphur properly. This report says:
So having too many Clostridia, producing too many phenols, will deplete the body’s reserves of sulphur. And sulphur is needed for other things — including brain development. If an unusual microbiome leads to the gut needing extra sulphur, the brain may pay the price by developing abnormally.
Like any other creatures, the bacteria that live inside us need to excrete, and they also produce poisons to defeat their bacterial rivals who compete for space and food. Just on their own, bacterial toxins cause inflammation.
Additionally, fat cells or adipocytes enter the picture and interact with bacterial byproducts, such as the lipopolysaccharide that oozes out of yet another species of gut bacteria, E.coli. Perturbed by these intrusions, the fat cells get busy producing cytokines, molecules that incite even more trouble, and pretty soon you’ve got a chronic inflammatory process with no end in sight.
“Autism: Inflammatory cytokines induce autoimmune reactions in the brain arresting right hemisphere development.” That sentence is from Dr. David M. Marquis, who goes on to say:
When antibodies combine with our structural proteins, specific genes are turned on in a special type of immune cell in the body. Inflammatory chemicals are created called cytokines, which are strongly damaging to brain function. In fact, elevated cytokines are seen in such devastating conditions as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and even autism.
A report on the impact of microbiota on the brain and behavior notes the increasing evidence that changes in the populations of gut microbes are associated with behaviors associated with cognition, pain, and even mood.
Dysfunction of the microbiome-brain-gut axis has been implicated in stress-related disorders such as depression, anxiety and irritable bowel syndrome; and neurodevelopmental disorders such as autism.
The controversial fecal transplant treatment is being tried on autistic kids in Arizona. It has also been suggested that microbes might some day be used to diagnose neurodevelopmental diseases. To finish up with, here is another autism-related quotation:
Although communication between gut microbiota and the CNS are not fully elucidated, neural, hormonal, immune and metabolic pathways have been suggested. Thus, the concept of a microbiome-brain-gut axis is emerging, suggesting microbiota-modulating strategies may be a tractable therapeutic approach for developing novel treatments for CNS disorders.
Your responses and feedback are welcome!
Source: “Seeking solutions, study explores autism-obesity link,” AutismSpeaks.org, 11/02/15
Source: “Me, myself, us,” Economist.com, 08/18/12
Source: “A ‘perfect storm’ for inflammation – bacteria and fat — may promote diabetes,” MedicalNewsToday.com, 11/04/13
Source: “How Inflammation Affects Every Aspect of Your Health,” Reset.me, 12/08/15
Source: “The impact of microbiota on brain and behavior: mechanisms & therapeutic potential,” NIH.gov, 2014
Photo credit: mikecogh via Visual Hunt/CC BY