There's an absolutely fascinating new paper by scientists at Ohio State University in the latest Cell. In short, the paper demonstrates that mice living in an enriched environments - those spaces filled with toys, running wheels and social interactions - are less likely to get tumors, and better able to fight off the tumors if they appear.
The experiment itself was simple. A large group of mice were injected with melanoma cells. After six weeks, the mice living in enriched environments had tumors that were approximately 75 percent smaller than mice raised in standard lab cages. Furthermore, while every mouse in the standard cages developed cancerous growths, 17 percent of the mice in the enriched enclosures showed no sign of cancer at all.
What explains this seemingly miraculous result? Why does having a few toys in a cage help prevent the proliferation of malignant cells? While the story is bound to get more complicated - there nothing is simple about cancer, or brain-body interactions - the researchers present a strikingly straightforward chemical pathway underlying the effect:
In short, the enriched environments led to increases in BDNF in the hypothalamus. (BDNF is a trophic factor, a class of proteins that support the survival and growth of neurons. What water and sun do for plants, trophic factors do for brain cells.) This, in turn, led to significantly reduced levels of the hormone leptin throughout the body. (Leptin is involved in the regulation of appetite and metabolism, and seemed to be down-regulated by slightly elevated levels of stress hormone.) Although a few earlier studies have linked leptin to accelerated tumor growth, it remains unclear how this happens, or if this link is really causal.
It's important to not overhype the results of this study. Nobody knows if this data has any relevance for humans. Nevertheless, it's a startling demonstration of the brain-body loop. While it's no longer too surprising to learn that chronic stress increases cardiovascular disease, or that actors who win academy awards live much longer than those who don't, there is something spooky about this new link between nice cages and reduced tumor growth. Cancer, after all, is just stupid cells run amok. It is life at its most mechanical, nothing but a genetic mistake. And yet, the presence of toys in a cage can dramatically alter the course of the disease, making it harder for cancerous cells to take root and slowing their growth once they do. A slight chemical tweak in the cortex has ripple effects throughout the flesh.
It strikes me that we need a new metaphor for the interactions of the brain and body. They aren't simply connected via some pipes and tubes. They are emulsified together, so hopelessly intertwined that everything that happens in one affects the other. Holism is the rule.
