microbiome - joe

Buffington et al vs. Reber et al

Seminar in BioPsych

Fall 2016

Professor Shansky

The most powerful implication of this week’s papers is the readily translatable conclusions, and moreover the fact that the authors addressed such a prominent issue in Western civilization. Normally, the abstract of papers includes a few sentences about the significance of this research. The great thing about these papers is that they were so different from the rest of papers we have read this semester; they spoke to the changes in Western culture (i.e. increases in obesity and detachment from certain bacterial environments in high-income families) and how those changes directly affected the gut — and indirectly the brain. It’s bizarre to think that the brain receives input from and is regulated by things as far detached as the gut. But indeed, the brain is an amazing piece of machinery.

I appreciated that both papers used very many measures to prove that this manipulation had far-reaching effects. Buffington et al used behavioral (social tests), biochemical (oxytocin and DA level characterization), genetic (gene sequencing for dysbiosis), and electrophysiological (recording firing patterns in reward centers) approaches, while Reber et al used similar approaches along with testing to see if this bacterium had other effects on the colon and immunity in general. This is an impressive set of experiments!

One thing I wondered was why Buffington et al showed that the effect they noticed was limited to reconstitution of live and not heat-killed bacteria, while Reber et al used heat-killed bacteria without addressing the potential effects of using live bacteria instead. I tried googling the difference in using either type of bacteria but I could not find a definitive answer. Furthermore, neither paper addressed the entire communication pathway between the gut and the brain, and so it was difficult for me to ascertain the gut’s modulatory effects on the brain, other than to see the implicit effects it was having on, say, LTP in the VTA (Buffington et al) or biosynthetic markers of 5-HT (Reber et al). The craziest — and most mysterious — element of these studies is that one change in the constitution of the microbiome can affect so many different things in the brain (from biogenic amine synthesis to inflammatory microglial response to firing pattern changes to downstream behavioral changes).

Reber et al remarked, when discussing the preventative effects of M. vaccae on stress-induced colitis, that “…immunization with M. vaccae, or similar bioimmunomodulatory approaches, may be useful for prevention of chronic stress/repeated trauma-induced inflammation and subsequent development of somatic and mental disorders,” to which I reply, “the future!” The papers we have gone through in the past few months have gradually opened my eyes to the magnitude of questions there still are to be addressed regarding the brain and its functions. Specifically, I have found that the multitude of ways that the brain can regulate itself as well as ways the environment can regulate it brings a plethora of questions that will keep the curiosity of scientists fueled for as long as my mind can conceive.