Exercise stimulates the genesis of new brain cells ... via the liver?

As we discussed in Beating the Dementia Monster, exercise stimulates production of the the BDNF protein, the brain derived neurotrophic factor.  BDNF plays a role in neurogenesis, prompting stem cells in the hippocampus to form new neurons.  It may also have a healing function for cells damaged by Alzheimer's disease.  How this works remains kind of mysterious.  But according the this week's ALZForum, some researchers at UC San Francisco found that, during exercise, the liver produces an enzyme that plays a role in the production of BDNF and may have other positive effects.  At least in mice.  They were able to link this with improved cognition in older mice.

Some suggest this points to a "liver-brain axis."

What's also interesting is that serum taken from exercising, older mice and delivered to sedentary mice appears to convey a positive effect to the sedentary mice, perhaps by carrying over the enzyme.

The enzyme is glycosylphosphatidylinositol-specific phospholipase D1. We’ll just call it Gpld1.

Gpld1 removes certain proteins from the surfaces of cells, but also suppresses the complement system, which is part of the body's immune response.  Isn't that bad?  But part of the immune response is inflammation, and, as we have discussed before, too much inflammation is bad.  Therefore, much of our effort to treat Alzheimer's disease is through reducing inflammation.  Diet, exercise, intermittent fasting, and getting good sleep can all contribute to reducing inflammation.  Apparently the production of Gpld1 is part of the story regarding how exercise can be associated with reducing inflammation in the brain, even though injury to the body during exercise has its own inflammatory response.

According to the article, there is a connection between neuroinflammation (inflammation in the brain) and peripheral inflammation (inflammation in the rest of the body).  But it's not well understood.  Gpld1 is a large molecule, and so it is blocked from involvement with brain chemistry by the blood-brain barrier.  The blood-brain barrier blocks pathogens from getting into the brain, but it also blocks antibodies and other large proteins.  So it's not clear how this Gpld1 is able to act on the brain, but it does appear to stimulate the production of BDNF, which is the main factor in my success in battling my disease.  In mice, at least, overproduction of Gpld1 in exercising mice increased production of BDNF by 40% and tripled the generation of new neurons.

There two things worthy of further consideration.  The first is the open question of whether what has been observed in mice reflects what occurs in the human body.  The second is whether the increased expression of Gpld1 from the liver can be stimulated pharmacologically in people too frail to exercise.  If so, that would be great.