On 2014 Dec 12, David Keller commented:

Parkinsonian constipation & altered gut microbiota: suggestions for further study

It has long been known that constipation due to autonomic dysfunction is an early pre-motor finding in Parkinson disease (PD). Other bowel motility disorders have been causally linked with alterations in gut flora; for example, opioid-induced constipation is a known risk factor for C. Difficile overgrowth (1,2), which in turn can cause diarrhea. If Parkinsonian constipation promotes changes in gut flora, it is reasonable to ask whether these changes in gut flora might alter the course of PD itself.

Do toxins produced by gut microbes contribute to CNS neurodegeneration in susceptible individuals? The serum levels of these toxins should be tracked in a study designed to measure their effects in PD. If overgrowth of certain toxigenic bacterial species appears to cause accelerated neurodegeneration, then treatment with antibiotics or probiotics (or both) should be tested in selected individuals, in an attempt to slow the progression of their PD.

References

1: Keller DL. Opioid use and clostridium difficile infection. Am J Med. 2013 Apr;126(4):e13. doi: 10.1016/j.amjmed.2012.08.024. PubMed PMID: 23507210.

2: Mora AL, Salazar M, Pablo-Caeiro J, Frost CP, Yadav Y, DuPont HL, Garey KW. Moderate to high use of opioid analgesics are associated with an increased risk of Clostridium difficile infection. Am J Med Sci. 2012 Apr;343(4):277-80. doi: 10.1097/MAJ.0b013e31822f42eb. PubMed PMID: 21934595.

On 2014 Dec 12, David Keller commented:

Parkinsonian constipation & altered gut microbiota: suggestions for further study

It has long been known that constipation due to autonomic dysfunction is an early pre-motor finding in Parkinson disease (PD). Other bowel motility disorders have been causally linked with alterations in gut flora; for example, opioid-induced constipation is a known risk factor for C. Difficile overgrowth (1,2), which in turn can cause diarrhea. If Parkinsonian constipation promotes changes in gut flora, it is reasonable to ask whether these changes in gut flora might alter the course of PD itself.

Do toxins produced by gut microbes contribute to CNS neurodegeneration in susceptible individuals? The serum levels of these toxins should be tracked in a study designed to measure their effects in PD. If overgrowth of certain toxigenic bacterial species appears to cause accelerated neurodegeneration, then treatment with antibiotics or probiotics (or both) should be tested in selected individuals, in an attempt to slow the progression of their PD.

References

1: Keller DL. Opioid use and clostridium difficile infection. Am J Med. 2013 Apr;126(4):e13. doi: 10.1016/j.amjmed.2012.08.024. PubMed PMID: 23507210.

2: Mora AL, Salazar M, Pablo-Caeiro J, Frost CP, Yadav Y, DuPont HL, Garey KW. Moderate to high use of opioid analgesics are associated with an increased risk of Clostridium difficile infection. Am J Med Sci. 2012 Apr;343(4):277-80. doi: 10.1097/MAJ.0b013e31822f42eb. PubMed PMID: 21934595.