A study I posted recently on the Facebook page generated a decent discussion on how traumatic brain injury promotes a leaky gut. The interesting take-home message from the study is that one long term symptom of traumatic brain injury(TBI) is “leaky gut”.
The theoretical trek from there is that endotoxin can then cross the gut wall and enter the bloodstream(called endotoxemia), cross the blood brain barrier because it is also “leaky” after TBI, and at least impede recovery from injury and at worst make the damage worse…far worse. In fact, the state this induces is not unlike what we see in Alzheimer’s disease and Parkinson’s disease, only in different areas of the brain. You can throw chronic traumatic encephalopathy(CTE) and possibly post- traumatic stress disorder(PTSD) in there as well.
True or not, this entire state is far from ideal for brain function and health. My personal thought about this is that some of these issues are merely a product of anti-resilience induced by our environment. I could certainly be wrong, but there’s some there there.
So that of course got me digging and my favorite gut-brain communication hormone popped up. I’m of course talking about me main man, the hunger hormone ghrelin.
Note: Since I just mentioned hunger I assume about 90% of you are ready to leave. I assumed the point of this blog, that hunger may have some physiological benefit would be met with the same receptiveness as a fart in church. Don’t leave, you want to read this.
Taken from: http://images.obesityhelp.com.s3.amazonaws.com/articles/wp-content/uploads/2016/04/ghrelin-760×434.png
Ghrelin and gut/brain communication
I recently blogged about ghrelin and how it may be a major player in helping sync the master circadian, stomach, and gut clocks together. You can find that blog here. Basically, ghrelin acts as a signaling molecule in the gut-brain axis and you would know that if you read the blog. 🙂
But it apparently goes a little further. So, we’ve known that the blood brain and intestinal barriers are regulated together, with the basic assumption being that this is done via butyrate-producing bacteria in the microbiome. But there’s another signaling molecule that does the same thing as butyrate via the same mechanism, and that something is ghrelin.
There’s further evidence for this effect of ghrelin, first in improving the blood brain barrier and next for the gut. It’s interesting to note that both studies used a traumatic brain injury to induce both conditions.
Another study used a sepsis model, aka endotoxemia, the aforementioned consequence of a leaky gut. In that study, ghrelin reduced systemic inflammation and leaky gut caused by endotoxemia. These effects of ghrelin happened through stimulation of ghrelin receptors in the brain with the vagus nerve functioning as a the puppet string the brain uses to regulate the gut. Confused yet?
Unfortunately, these studies were in mouse models and used injections of ghrelin rather than endogenous secretion. A study doing this in mice would be very complex and difficult to do while controlling extraneous variables.
Ghrelin-The redheaded stepchild of gut-brain hormones
With these powerful, albeit potential, effects of ghrelin, you’d think that people would be in love with it. Unfortunately, no one likes ghrelin because it makes them hungry. In fact, most of us have an aversion to the sense of hunger that served us well when food was scarce.
Just because we assign a negative emotional value to ghrelin doesn’t mean that it isn’t providing some form of physiological benefit or benefits. Generally, things that we are averse to we avoid for a reason, like the sensation of pain we experience when putting your hand in a fire. But I wouldn’t view ghrelin as one of these things as its primary effect is to get us to move around and find food. It’s saying, “Get off your dead ass and find food!”. So while the emotion is negative, there may be some benefit to regularly experiencing it.
This brings up a few good points/questions:
- Is ghrelin and the hunger it induces telling us our brain and gut are communicating well and our blood brain and intestinal barriers both pretty secure?
- Does this imply that those of us who rarely experience hunger are more prone to disruption of the blood brain and intestinal barriers? Would explain the increase in endotoxemia in Type 2 diabetics.
- Does our avoidance of hunger via constant food orgy increase our risk for brain related issues such as Alzheimer’s, Parkinson’s, CTE and PTSD?
These are interesting questions that I hope we eventually get answers to. Until then, I’ll continue to regularly experience hunger and embrace it.