To ensure that this reaction was not based exclusively on rodents, the scientists also analyzed the extraction of blood from older people. Older men and women who routinely walked for exercise showed higher levels of GPLD1 in the bloodstream than those who did not.
The combined result of these findings appears to be that exercise improves brain health in part by causing the liver to pump additional amounts of GPLD1, says Dr. Villeda, although how the protein changes the brain is still unclear. Subsequent experiments by the scientists showed that the protein probably does not break the blood brain barrier and acts directly on the brain, says Dr. Villeda. Instead, it is likely to cause disturbances in other tissues and cells in other parts of the body. These tissues, in turn, produce even more proteins that have effects on other tissues that eventually lead to direct changes in neurotransmitters, genes, and cells in the brain that underpin cognitive improvements.
Dr. Villeda believes that if more experiments show that GPLD1, in isolation, helps initiate this molecular chain reaction, then at least it is conceivable that infusions of the substance may offer the brain benefits of exercise to people who are too much fragile or disabled for regular physical activity
However, this experiment involved primarily mice, not people, and tells us nothing about the systemic effects of additional GPLD1, which in large amounts might be undesirable. More fundamentally, the findings highlight the pervasive, intricate, and body-wide effects of exercise, with the liver, in this case, somehow changing minds and brains after workouts. At the moment, it is impossible to know whether the same synchronized and intertwined processes would occur in response to an GPLD1 exercise pill and, if not, whether it could be considered an exercise pill.
Dr. Villeda is quick to accept that pharmaceutical GPLD1, even if it is effective for brain health, “would not recapitulate the benefits of exercise.” There would be none of the usual fat burns, muscle development, or cardiovascular improvements, he notes. But he hopes that if future experiments in his laboratory on animals and people show consistent results, the substance could eventually help people who have trouble thinking better.
