Strong body helps the mind

A good workout doesn’t just make the body stronger. It also produces a chemical that may keep depression away, scientists report. Their findings come from a new study of mice and another in a small group of people. Doctors have often prescribed exercise to help treat people with depression. The new data points to why that can work.

“This paper really emphasizes ‘strong body, strong mind,’” Andrew Miller told Science News. A psychiatrist at Emory University in Atlanta, Ga., Miller did not work on the new study.

The researchers mapped out the protective activity of one chemical that the body makes during exercise. These data may help explain why exercise can heal a person in different ways, Miller says. The study also may point to new ways to treat brain disorders, he adds.

After a good workout, muscles produce a chemical called PGC-1 alpha 1. Scientists already knew that this stuff acts like a molecular Good Samaritan. It signals the body to make more blood vessels and more mitochondria (My-toh-KON-dree-ah). Those mitochondria are important features of cells. They convert food into the energy that powers cells.

The new study shows that this ramp up in PGC-1 alpha 1 has benefits that reach all the way to the brain. In one set of tests, the scientists exposed mice to several things that cause stress. For instance, they cut back on how much food the mice got to eat. They also exposed the animals to strobe lights and loud noises. After five weeks, the stressed mice showed signs of depression. Their symptoms: They consumed less sweet water and did not try to swim when placed in a tank of water.

The researchers then conducted the same tests on mice that had been genetically altered to produce high levels of PGC-1 alpha 1. These mice did not show signs of depression after five weeks of stress. “Nothing happened,” said Maria Lindskog, a neuroscientist at the Karolinska Institute in Stockholm, Sweden. The animals seemed unaffected, she told Science News. It appeared, she concluded, that “the brain was completely protected.”

But her team didn’t stop there. They turned to a chemical called kynurenine (KY-nure-EN-een) that the body produces during stress. When they injected this chemical into their mice, the animals showed signs of depression — such as drinking less sweet water.

But the researchers found that PGC-1 alpha 1 helped transform kynurenine into a different chemical. That new chemical had trouble reaching the brain. So mice whose muscles had produced high levels of PGC-1 alpha 1 no longer became depressed. These animals seemed immune to the negative effects of kynurenine. The scientists found that PGC-1 alpha 1 protected their brains from depression.

The new study shows that muscles can have a strong influence on other organs, Lindskog told Science News. Muscle, she concludes, “is like a detoxifying organ.”

Her team looked for the same effects in people. After volunteers exercised for three weeks, their muscles produced PGC-1 alpha 1 and other chemicals that helped lower kynurenine levels in the brain.

The study may point to better treatments for depression. Some people may benefit strongly from more exercise, Miller says, or from drugs that stop toxic compounds from getting to the brain.

Power Words

amino acids  Simple molecules that occur naturally in plant and animal tissues and that are the basic constituents of proteins.

cell   The smallest structural and functional unit of an organism. Typically too small to see with the naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere from thousands to trillions of cells, depending on their size.

chemical      A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H₂O.

depression  A mental illness characterized by persistent sadness and apathy. Although these feelings can be triggered by events, such as the death of a loved one or the move to a new city, that isn’t typically considered an “illness” — unless the symptoms are prolonged and harm an individual’s ability to perform normal daily tasks (such as working, sleeping or interacting with others). People suffering from depression often feel they lack the energy needed to get anything done. They may have difficulty concentrating on things or showing an interest in normal events. Many times, these feelings seem to be triggered by nothing; they can appear out of nowhere.

mitochondria  (sing. mitochondrion) A structure in all cells (except bacteria) found outside of their nuclei. Here the cell breaks down nutrients and converts them into a form of energy known as ATP.

molecule  An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O)

muscle  A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in a protein, which is why predatory species seek prey containing lots of this tissue.

neuroscience  Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.

organ     (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that interprets nerve signals and a plant’s roots are organs that take in nutrients and moisture.

proteins      Compounds made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. The hemoglobin in blood and the antibodies that attempt to fight infections are among the better known, stand-alone proteins.Medicines frequently work by latching onto proteins.

psychiatry    A field of medicine where doctors study and treat diseases of the human mind. Treatments may consist of talking therapies, prescription drugs or both. The medical doctors who work in this field are known as psychiatrists.

stress  (in biology) A factor, such as unusual temperatures, moisture or pollution, that affects the health of a species or ecosystem. (in physics) Pressure or tension exerted on a material object.

toxic  Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

tryptophan     An amino acid needed for the growth of babies and to keep the levels of nitrogen in the adult body in balance. It is essential for health but cannot be made by the body. It must come from the foods we eat.