‘Lazy’ mice that received blood from more athletic congeners had important neurological benefits. They performed better on memory tests and were better protected against symptoms of diseases such as Alzheimer’s.
It is well known that exercise is good for the brain. It now appears that these benefits are transferable to mice by means of a blood transfusion. A large part of these health benefits can be traced back to clusterin, a protein that occurs in higher concentrations in athletes.
Researchers at Stanford University in the United States allowed three-month-old mice to live in cages with or without a wheel for a month. In cages with a wheel, mice run about 6 to 9 kilometers a day, while mice in cages without a wheel do not cover nearly that distance. After a month, the running mice had clearly more neurons in their brains than the lazy mice.
The researchers then took blood from both groups. They gave the lazy mice a blood transfusion equal to 8 percent of the total blood volume every three days. One group of lazy mice was injected with ‘sporty’ blood, and a second group was given ‘lazy’ blood. Four weeks and nine blood transfusions later, the researchers had the two groups do two memory tests. The mice that received the riders’ blood scored better on both tasks than the mice with lazy blood.
The mice with sporty blood also had more new neurons in the hippocampus. This brain region is closely involved in memory and navigation.
To determine the causes of these changes, the researchers looked at the protein composition of both blood types. They found a total of 235 proteins in the mouse blood, of which 23 protein types were less and 26 more were present in the sports blood than in the lazy blood.
When the researchers looked at the influence of these proteins, they saw that one protein was largely responsible for the health benefits. This protein, called clusterin, was more abundant in sports blood. Removing this protein from sports blood was also found to remove almost all benefits.
Further research into how this protein works showed that it binds strongly to receptors that are common in the blood vessel walls in the brain. These receptors are often inflamed in Alzheimer’s patients. To make the causal link even stronger, the researchers used genetic modification to induce Alzheimer’s symptoms in a new group of mice. The administration of clusterin was found to have an inhibitory effect on these symptoms.
In another study conducted by the same research group, twenty veterans who had memory problems at a young age followed a six-month sports program. The clusterin levels in their blood also rose.
Paul Lucassen, neuroscientist at the University of Amsterdam, finds the research interesting, but also has reservations. ‘Similar research has been done before into the effects of blood transfusions in animals. For example, research has already been done into the effects of blood transfusions between young and old mice. This also indicated an important role of blood in aging. That they have now done this in relation to physical exercise is innovative. It is also interesting that they have analyzed this effect down to the molecular level. The fact that clusterin plays such a prominent role in this is also new.’
A downside, he says, is that it has not been studied how long the benefits last, and what lazy blood would do in mice that exercise. ‘The effects in the hippocampus should be determined over a longer period of time to see how strongly the number of neurons really grows, and what their actual contribution is.’
According to Lucassen, conducting this experiment on humans would encounter too many ethical and technical objections. ‘If you administer large blood volumes to people for a long time, there is a risk of side effects and complications. But it would be interesting to look at the effects of administering clusterin in people with memory complaints or Alzheimer’s.’