How does exercise prompt fat to benefit metabolism?
14 February, 2019
An international team of scientists has uncovered molecular evidence of how exercise benefits metabolism and health through its effect on fat. The evidence reveals that fat plays an active role in the process.
The finding follows earlier work in which the researchers were the first to show that exercise prompts fat tissue to release molecules that regulate metabolism.
Now, in a new paper that appears in the journal Nature Metabolism, they describe how they identified one of these molecules and investigated its activity.
The molecule is a protein called transforming growth factor beta 2 (TGF-beta 2) and the study concerns its effects on glucose and fatty acid metabolism.
Using mice, the researchers demonstrated that exercise stimulated fat cells to release TGF-beta 2, which improved glucose tolerance.
In addition, treating sedentary mice with TGF-beta 2 reversed "the detrimental metabolic effects of high-fat feeding" in the animals.
"The fact," says corresponding study author Laurie J. Goodyear, Ph.D., a professor of medicine at Harvard Medical School in Boston, MA, "that a single protein has such important and dramatic effects was quite impressive."
Adipokine improves glucose tolerance
TGF-beta 2 is an adipokine, which is a large group of signaling proteins that originate primarily in fat cells, or adipocytes.
Adipokines help regulate a variety of metabolic processes in fat tissue and also in the brain, liver, and other organs. They also have a role in the immune system.
TGF-beta 2 is unlike most of the adipokines that fat cells release, which tend to increase with obesity and can harm health and metabolism.
Prof. Goodyear explains that "[i]n contrast to the negative effects of many adipokines," their study identified TGF-beta 2 as an adipokine that "actually improves glucose tolerance" when it is released from fat cells as a result of exercise.
She and her colleagues investigated adipokines in male humans and mice before and after exercising. They saw that levels of TGF-beta 2 went up after exercise.
Further investigation revealed that — both in the men and mice — exercise caused TGF-beta 2 levels to rise, not only in fat tissue but also in the blood.
The team also learned that treating mice with TGF-beta 2 directly triggered metabolic changes, including higher levels of fatty acid uptake and better glucose tolerance.
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