This is a frantic time for the stomach bug. The heat, lowered
water levels and vacationing crowds bring a host of stomach infections with
them. Many of you like me might have already suffered. After a few days of antibiotics
and food restrictions we get better. We no longer give a thought to the
bacteria in the gut, except with a sense of passing annoyance.
But these little guys in your stomach might be far more
important than we think (or don’t think). If the hints scientists are getting
turn out to be correct, gut bacteria (or microbiome, as they are called), might
be having profound effect on the development of our brains and our mental well
being.
In some interesting experiments on mice, researchers found
clear links between microbiome and anxiety. They delivered some baby mice
through caesarean procedure. Such mice had a different microbiome from the baby
mice born though vaginal delivery, who acquired the vaginal bacteria of their
mothers. The researchers found that the caesarean born mice had higher anxiety
levels than the normally born mice. It’s too early to link this observation to
human beings, but this just points out the kind of discoveries we might make.
Some studies are happening on human beings. After the 2000
flooding of many Canadian regions, more than 2000 people were affected by
gastrointestinal problems, such as irritable bowl syndrome (IBS). Researchers
studying the affected people found a clear correlation between psychological
disorders such as depression and anxiety and IBS. Scientists are working on the
question of whether the destruction of gut bacteria due to infection caused the
mental disorders. Links of gut bacteria with disorders like autism have already
been seen.
(See my 2013 article : http://www.yourssciencely.in/2013/12/gut-bacteria-and-autism.html)
The obvious question is: how can bacteria in stomach affect
the brain? Microbes in blood cannot enter the brain cells due to what is called
as the blood-brain barrier. Some microbes like the Rabies virus break this
barrier and enter neurons, playing havoc with us such as making us afraid of
water among other things.
But gut bacteria mostly do not take such drastic steps. They
have other powerful weapons at their disposal. The waste products of many gut
bacteria contain neurotransmitters, the chemicals that our brain cells use to
talk to each other. An example is the neurotransmitter Serotonin. Scientists
found that levels of Serotonin in blood change significantly when microbiome is
changed. This might be affecting our brains.
Gut bacteria might also be have other complex effects on the
development of baby brains. As an example, they might be affecting a process
called Myelination, a kind of covering up of neurons. The chemicals produced by
these bacteria might be triggering growth of neurons in particular places in
the young brains.
Finding these links is important because then we can use them
for treatment. An interesting research is going on at the McMuster University,
Ontario in Canada. The Office of Naval Research has funded a research project to
find a treatment that will help soldiers deal with stress better. The fighters
have to face several high-stress situations in their work. It is possible that
supplementing them with proper gut bacteria might improve their stress handling
capability. I think we might all benefit from such a discovery!
Naturally, the pharmaceutical industry sees a big
opportunity in this research. Since 2008, more than 500 million dollars have
been spent in finding microbiome based treatment for mental disorders. We haven’t
seen much success yet, but some good breakthroughs may be just round the
corner. Of course, ‘Probiotic’ yogurt and probiotic supplement tablets are
already here. But though harmless, they haven’t been found effective in
anything.
This might change very soon as we understand the links
between gut bacteria and brain (called the microbiome-gut-brain axis) better. I
would love to report the progress as it is published.
