Running from cancer

Sports as medicine

Fyodor Galkin, "Biomolecule"

Sport is a mandatory component of a healthy lifestyle. Everyone knows the positive effect of sports on the cardiovascular system and muscle tone. But in recent years, there have been reports of completely unexpected effects of physical exercise: sports help with cancer, mental disorders and neurodegenerative diseases.

Adrenaline and interleukin-6 released during muscle exertion mobilize natural killer cells that penetrate the tumor and prevent its development.

In the modern world, people lead a predominantly sedentary lifestyle. Sports can neutralize the harm of inactivity, which leads to obesity, thrombosis, tachycardia and fatigue. But the benefits of sports are not limited to these universally known facts. Every year scientists find new evidence that physical activity prevents the development of diabetes, cancer and nervous disorders. Revealing the mechanisms that provide these beneficial effects of exercise is a promising direction in molecular biology.

Running from cancer

Danish scientists have demonstrated a mechanism by which exercise slows down or even completely prevents the development of malignant tumors. Science has come closer to understanding the complex relationship between oncogenesis and the immune system.

Playing sports is primarily stress. But not psychological, but cellular. When performing physical exercises, muscles release a lot of hormone–like proteins - cytokines into the blood. Some of these substances can independently suppress the development of certain types of cancer, but so far it has been possible to show this only indirectly: experiments were conducted either on cell cultures or on healthy animals.

The effect of exercise was tested by Danish biologists on five mouse models of cancer. In all cases, the effect was strictly positive. For example, four weeks of running in a wheel (an average of 4 km per day) before a melanoma transplant slowed tumor growth by 61% (Fig. 1). In the Lewis lung carcinoma model, running halved the volume of the tumor and prevented weight loss. Running also almost halved the incidence of liver cancer when the carcinogen diethylnitrosamine was injected into the blood [1].

Figure 1. The introduction of melanoma cells into the bloodstream leads to the development of metastases in the lungs. Mice that ran daily before the injection (right) have much smaller tumors than sedentary mice (left). Figure from [1].

Previously, in human studies, scientists have also repeatedly shown the benefits of physical exercise for different types of tumors, but the limited methods did not allow us to look into the mechanism of this phenomenon [2]. Mouse models give experimenters much more freedom of action.

Differential analysis of gene expression in exercise and sedentary mice revealed 92 genes, many of which are involved in immune response reactions. Immunity in oncology is an ambiguous thing: on the one hand, it helps to fight the tumor, but on the other – chronic inflammation can worsen the prognosis. Many cancer studies are aimed at creating conditions in which the immune response has only a positive effect.

It seems that physical activity creates just such conditions. In proven models, due to the adrenaline released during running, natural killers leave the spleen, and the IL6 cytokine promotes their infiltration into the tumor, where they destroy cancer cells. At the same time, the two substances act synergistically: the introduction of adrenaline into the blood only partially repeats the effect of running, and IL6 alone does not act at all [1].

Most likely, a similar mechanism works in humans. So now there are one more reasons to play sports.

Brain charging

Sport also improves a person's mental state. Previously, it was believed that this was due to purely sociopsychological factors. Sports are approved by society, which helps a person feel normal. Some people use sports as a way to distract themselves from problems. In addition, increasing the tone of the body allows you to overcome chronic fatigue associated with depression, and gaining muscle mass or losing weight provides a reason for pride [3].

But as it turns out, physical exercises do not affect the nervous system so indirectly. In people suffering from depression and Alzheimer's disease, both in the blood and in the brain, the level of the neurotrophic (neurotropic) factor of the brain (brain-derived neurotrophic factor, BDNF) is lowered. Physical activity increases the concentration of BDNF in the blood, muscles [4] and brain [5]. An increase in the level of BDNF in the brain of running mice is associated with an improvement in spatial thinking [6] and promotes the division of neurons in the dentate fascia – the part of the hippocampus responsible for episodic memory and bad mood (Fig. 2). At the same time, BDNF in the hippocampus increases the expression of proteins involved in memory mechanisms [7].

Figure 2. In mice running in a wheel, hippocampal neurons divide more actively.a, b – Micrographs of the hippocampus of sedentary and running mice.
Dividing cells are shown in black (immunohistochemistry on BrdU four weeks after administration). c, g – Fluorescent labeling of hippocampal cells: green – nerve cells, blue – glial; dividing cells – red.
d – Counting from microphotographs showed that running mice have twice as many dividing cells in the dentate fascia of the hippocampus than sedentary mice.

BDNF is not the only mediator between sports and good mood. Athletes during a long run report a sudden feeling of lightness and euphoria. Runner's euphoria (a phenomenon known in the English-speaking world as "runner's high") is associated with the production of endocannabinoids during running in both the peripheral and central nervous systems. The molecular mechanisms of this phenomenon were tested on mice that showed reduced anxiety and pain sensitivity after running. Unfortunately, it was not possible to quantify the actual euphoria in mice [8].

Sports contribute to stress resistance. Psychological stress leads to the release of the hormone cortisol into the blood. During physical exertion, cortisol is also produced, which during several hours of rest is converted into an inactive form – cortisone [9, 10]. With psychological stress, on the contrary, cortisol accumulates in the body. Chronically elevated cortisol levels lead to anorexia, hypertension, hyperglycemia and depression. Cortisol inactivation, which occurs in trained people, helps them to tolerate nervous tension more easily and relieves its consequences.

When George Foreman regained the title, it really hit a nerve with me. I also wanted to go back.
But then the morning came – it was time to go for a run. I got back into bed and said, "Okay, I'm still the greatest."

Muhammad Ali

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Portal "Eternal youth" http://vechnayamolodost.ru  06.04.2016