Antihistamines affect exercise recovery, may or may not be a problem

http://www.eurekalert.org/pub_releases/2016-04/uoo-aae041416.php

Public Release: 14-Apr-2016
Antihistamines affect exercise recovery, may or may not be a problem
University of Oregon research identifies 3,000 genes that are busy after exercise, including 795 that are altered by strong doses of histamine blockers
University of Oregon

After vigorous exercise, some 3,000 genes go to work to aid recovery by boosting muscles and blood vessels, but in the presence of high doses of antihistamines almost 27 percent of the gene response is blunted, according to University of Oregon researchers.

Whether the antihistamine effect on 795 affected genes might suggest a problem for competitive athletes and devoted exercisers, however, is not known, said John R. Halliwill, professor of human physiology. He was one of 10 co-authors of the study now online ahead of print in the Journal of Physiology.

Histamine is a substance in the body that responds to pollens, molds, animal dander, insect bites and other allergens. Too much response in some people fuels uncomfortable allergic reactions, prompting the use of antihistamines.

Halliwill discovered in 2005 that histamines also relax blood vessels, increasing blood flow that aids post-exercise recovery. That emerged from his original focus on why some people, including athletes, pass out after vigorous physical exertion. He later found a link between an over-activation of two histamine receptors to drops in blood pressure.

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The antihistamines had no effect prior to exercise and little influence on gene expression at the conclusion of the workout. Three hours after exercise 88 percent of the 795 genes affected by the antihistamines mostly responded with lower levels of expression.

"Histamine, a substance that we typically think of negatively and is most often associated with seasonal allergies, is an important substance contributing to the normal day-to-day response to exercise in humans," said Romero, who is now at the University of Texas Southwestern Medical Center in Dallas on a postdoctoral fellowship from the National Institutes of Health.

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A key question is whether people should avoid taking antihistamines when they exercise. It's too early to make that call, Halliwill said.

"We've got more work that we have to do," he said. "We need to do a training study in which we put people on histamine blockers and see if their adaptations to exercise training are as robust or diminished. There are a lot of redundancies in physiological systems. I wouldn't be surprised if blocking histamine receptors ends up being overcome by something else, but I also wouldn't be surprised if we can demonstrate that some responses to exercise training do become blunted if you take high doses of histamine blockers."