- A recent study found that high intensity aerobic exercise increased glucose consumption by internal organs.
- The researchers believe this association reduces the availability of energy needed for tumors to grow.
- Using data from a prospective study, researchers found 72% less metastatic cancer in participants who regularly engaged in high intensity aerobic activity.
- In another study involving mice, researchers found that aerobic activity reduced the development of metastatic tumors in the animals’ lymph nodes, lungs, and livers.
Metastatic cancer is cancer that has spread from where it started to another part of the body.
Researchers behind a 2022 study estimated that 623,405 individuals in the United States were living with metastatic breast, prostate, lung, colorectal, or bladder cancer, or metastatic melanoma in 2018.
While working with other researchers, Prof. Carmit Levy, Ph.D., associate professor of human molecular genetics and biochemistry at Tel Aviv University, became interested in how muscle is resistant to metastatic cancer.
That work led to a new study from Tel Aviv University, recently published in Cancer Research, which suggests people may be able to reduce their risk of developing metastatic cancer by regularly engaging in high intensity aerobic exercise.
“From [being curious] about the muscle, we ended up investigating physical activity,” Prof. Levy told Medical News Today. “We said, ‘OK, there’s something about the activity of the muscle that maybe protects this organ from being a common site for metastasis for all types of cancers.’”
With their work, the researchers identified the mechanism behind the preventive effect of exercise. They found that physical activity increases glucose consumption by internal organs, which means less energy available to the tumor.
Erica Rees-Punia, Ph.D., MPH, a senior principal scientist in epidemiology and behavioral research at the American Cancer Society, not involved in the study, described the underlying mechanism to MNT:
“Simply put, exercise ‘reprograms’ our organs to require more nutrients. At the same time, healthy organs of exercisers are more easily able to outcompete cancer cells (specifically melanoma cells, in the case of this study) for nutrients. This leaves fewer nutrients available for the tumor to use to grow.”
Studying the effects of exercise in cancer-free individuals
For the study, Prof. Levy and Dr. Yftach Gepner, senior lecturer in the School of Public Health at Tel Aviv University, combined data from a prospective study conducted by the Israel Center for Disease Control and the Nutrition Department of the Israeli Ministry of Health.
They looked at 2,734 men and women selected from the Israeli general population who were originally cancer free and between the ages of 25 and 64 who were examined before and after running.
Participants responded to two physical activity questionnaires about vigorous and moderate activity that lasted for 10 minutes. They were followed over a 20-year period.
Additionally, researchers recruited 14 male and female runners ages 25 to 45.
Participants were excluded for being smokers, taking prescribed medications, or having a history of chronic pulmonary, cardiac, metabolic, or orthopedic conditions.
They were also asked to avoid caffeine for 12 hours, food for 3 hours, and strenuous physical activity for at least 24 hours before arriving at the laboratory for testing.
Participants ran for 30 minutes on a treadmill at the highest speed they could manage for the entire duration.
Next, researchers collected ventilator and metabolic measurements using breath-by-breath analysis and monitored the heart rate of participants using a chest strap. They collected blood from the participants before and after they exercised.
Effects of exercise on metastatic cancer in mice
In another study, the researchers used an animal model where mice were subjected to exercise regimens.
They selected female mice because they’ve shown an increased metabolic response to exercise compared with males.
One group of mice was used as a control. The other was subjected to an exercise training protocol on a treadmill. Mice exercised every other day. Gradually, the researchers increased the duration and intensity of the exercise. This went on for 8 weeks.
Some of the mice were then injected with melanoma cells. After 4 days of recovery, researchers again subjected these mice to regular exercise on the treadmill for 4 additional weeks.
Later, researchers harvested the lungs, lymph nodes, livers, and skeletal muscles of both sedentary mice and mice subjected to exercise for proteomic and ex vivo metabolic capacity analyses.
“We took organs that usually host metastasis,” Levy told MNT.
“And we said, ‘Let’s dissect those organs and see how these organs behave after long-term physical activity.”
Impact of exercise on internal organs
Proteomic analysis of the blood of the routinely active participants showed increased carbohydrate usage after exercise.
Data from the prospective study showed that exercise prior to developing cancer had a modest impact on diagnoses of slow-growing cancer.
However, exercise “significantly reduced the likelihood of highly metastatic cancer,” according to the researchers.
Among the participants studied, those who reported regular aerobic exercise at high intensity had 72% less metastatic cancer than sedentary participants.
In the mouse study, researchers found that mice subjected to exercise prior to being injected with cancer cells were “significantly protected” against metastases in distant organs.
Proteomic and ex vivo metabolic capacity analyses of the mice organs showed that exercise induces catabolic processes, glucose uptake, mitochondrial activity, and GLUT expression.
When researchers looked at the mice organs, they discovered that long-term physical activity changes muscles (increasing muscle mass) and changes organs.
“We discovered that internal organs like lymph nodes, like lung, like liver, those organs that are usually hosting cancer [are] changing when there is chronic physical activity,” Levy told MNT.
“They change in [the] sense that they become super metabolic. And when I say super metabolic, I mean their demand for glucose and demand for their mitochondria is increasing [and] their glucose uptake is increasing. They’re becoming like superhero organs.”
When cancer attempts to attack these organs, it loses the fight, the researchers believe.
Dr. Adrian Cristian, chief of cancer rehabilitation at Miami Cancer Institute, part of Baptist Health South Florida, explained to MNT that with this study, the researchers demonstrated “that exercise induces changes in the micro-environment of cancer cells that make it inhospitable for them to grow when they are out-competed by non-cancer cells for nutrients.”
Areas for future study on exercise and metastatic cancer
In future research, Levy told MNT, researchers could look at whether exercise needs high intensity to gain the protective effect.
“What we were studying here was aerobic,” Levy noted. “I’m not saying that Pilates is not doing the same. I just don’t know because we haven’t studied other [types] of physical activity.”
Researchers who worked on this study are also interested in looking at how exercise impacts people who already have cancer, as well as how long the preventive effect of exercise lasts when people stop regularly working out.
“For how long does the body remember? We don’t know,” Levy said.
Currently, the authors of the present study are looking at how physical activity impacts brain metastases.
According to Dr. Cristian, more research is needed on how exercise impacts the metastatic spread of common cancers, like breast, prostate, colorectal, lung, and gynecologic cancers.
“Which cancers are more sensitive to exercise as an intervention to minimize metastatic spread,” Dr. Cristian said.
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