A hormone in the bloodstream that can rise sharply in exercise as well as in cold, could eventually lead to treatments for obesity, finds a study.

Experiments in both humans and mice have shown that levels of one lipokine, with the unwieldy name of 12,13-diHOME, climb significantly in exercise, unlike the levels of other lipokines analyzed.
The study followed up on research published last year in joint work with the lab of Joslin's Yu-Hua Tseng, Ph.D. This collaboration explored the release of lipokines from brown fat, which can burn energy in people or other mammals exposed to cold. In both humans and mice, the researchers demonstrated that the 12,13-diHome molecule was released from brown fat during cold exposure and offered beneficial metabolic effects.
"We found it very striking that when we then analyzed lipokines in exercise, the same lipokine that increased with cold also increased with exercise," says Goodyear, an Associate Professor in Medicine at Harvard Medical School.
The Joslin researchers began by measuring levels of lipokines before exercise, immediately after exercise and three hours after exercise in the blood of 27 healthy male volunteers of various ages. When measured immediately after exercise, "12,13-diHOME really stood out quite dramatically," says Goodyear.
The scientists followed up by studying another set of volunteers, 12 healthy young people (split evenly between women and men) without regular exercise routines. Again, levels of the lipokine generally climbed substantially during exercise. Additionally, the scientists found that, in general, the more fit people were, the greater their resting levels of 12,13-diHOME.
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Next, the investigators looked at molecular clues to the source of the lipokine and discovered that brown fat was a likely suspect. This was confirmed when the scientists removed most brown fat from mice and found that 12,13-diHOME levels in exercise dropped sharply. "It seems to be the first example of a hormone released from brown fat that might regulate some of the metabolic effects of exercise," Goodyear notes.
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Further work in both mice and mice muscle cells that were given 12,13-diHOME revealed that the lipokine acts as a signal to boost the use of fatty acids as fuels, Goodyear adds.
She and her colleagues are broadening and deepening their research on the role of the lipokine, and other lipokines that decrease during exercise, in larger human cohorts as well as in further animal studies. "The more knowledge we have about exercise and how it works, the better we can understand how to combat metabolic disease," she says.
Source-Eurekalert