I remember first reading about Dr. Braak almost two decades ago.  He proposed then that Parkinson’s disease may be a “gut” outcome.  Yes, I know it’s a brain disorder, but Braak thought it started in the gut and traveled to the brain.  (This theory has become known as the Braak hypothesis.)

I reported last year on other folks found that the vagal nerve may be just the way the alpha synuclein can make its way to the brain.  Now, Dr. Ted Dawson (Johns Hopkins Medical), the lead author of this new research, published new results in Neuron (Transneuronal Propogation of Pathologic α-Synuclein from the Gut to the Brain Models Parkinson’s Disease).  His co-authors includes Drs. S. Kim, S-H Kwon, T-I Kam, N. Panicker, S.S. Karappagounder, S. Lee, J.H. Lee (now at Alabama Medical), W.R. Kim, M. Kook. C.A. Foss, C. Shen (now at Shanghai Jiao Tong University, Shanghai), H. Lee, S. Kulkarni, P.J. Pasricha, G. Lee, M.G. Pomper, V.L. Dawson, and H.S. Ko.

These folks created an animal model, injecting various proteins (alpha-synuclein preformed fibrils) into the stomachs (pylorus, contiguous to the vagal nerve) of mice.  It took about a month before the symptoms of Parkinson’s disease manifested.  This confirmed that the disease can travel from the gut.

Note that they used exogenous (external or foreign to the body) alpha-synuclein.  But that’s not what made its way to the mouse brain.  No, the exogenous synuclein causes the endogenous (normal, within the body) synuclein to misfold and then transmit the problem compounds.  And, if the researchers performed a vagotomy (the removal of the vagal nerve), no synuclein transferred to the brain and Parkinson’s was not manifested.

The mice manifested Parkinson’s symptoms that were not just shaking etc. (the motor features of Parkinson’s), but even the non-motor functions.  Anxiety, depression, cognitive dysfunction, smelling disorders were detected.

This means that the Braak hypothesis is probably correct.  But, more importantly, for the first time, we have a viable animal model to test treatment for Parkinson’s.

But, it doesn’t mean this is the way Parkinson’s will always start in humans.

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