January 02, 2014

Researchers evaluate mechanisms of anabolic steroids in feedlot steers


January 2, 2014 – Anabolic steroid implants have improved muscle growth in beef cattle. However, very few studies have evaluated the mechanisms that cause muscle growth. For a new article published in the Journal of Animal Science, researchers studied the mechanisms involved in anabolic steroid-enhanced muscle growth in beef cattle including the role of satellite cells.

Dr. William Dayton, animal science professor at the University of Minnesota, evaluated the impact of satellite cells in anabolic steroid-stimulated muscle growth in feedlot steers. He said that satellite cells proliferate and fuse into the muscle fibers to provide nuclei needed to support postnatal muscle growth.

According to the researchers, muscle fiber number in cattle is determined before birth, and postnatal muscle growth occurs by increasing the size of existing fibers. Because the nuclei in muscle fibers do not divide, fiber growth requires addition of nuclei acquired from satellite cells. However, the number of satellite cells decreases as the animal reaches maturity, and this limits muscle growth.

“When we did muscle biopsies, we saw that there were more satellite cells in the muscle tissues from the animals that have been implanted,” Dayton stated.

Dayton said this finding lead them to believe that anabolic steroid implants stimulate satellite cell proliferation, resulting in more satellite cells to support muscle growth. Experiments under controlled conditions in satellite cell cultures confirmed that both trenbolone acetate (a testosterone analog) and estrogen stimulated satellite cell proliferation.

“As a part of those studies, we started looking at mechanisms that you can use to actually silence or shut off specific receptors in the cells and assessed whether silencing specific receptors affected the response of satellite cells to estrogen,” Dayton stated. These studies allowed the researchers to examine the role of specific receptors in the effect of estrogen on satellite cell proliferation.

Dayton said these studies have shown that in addition to the classical estrogen receptor (estrogen receptor-alpha) other receptors such as the insulin-like growth factor-1 receptor are also involved in estrogen response in the muscle.

Dayton said their research is funded by an Agriculture and Food Research Initiative Grant from the USDA National Institute of Food and Agriculture. He said if we can understand mechanisms of anabolic steroid-enhanced muscle growth, then we will be able to target muscle growth more effectively.

This article is titled “MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM—Role of satellite cells in anabolic steroid-induced muscle growth in feedlot steers.” It can be read in full at the journalofanimalscience.org.

Scientific Contact:
Dr. William Dayton
University of Minnesota

Media Contact:
Laci Jones
American Society of Animal Science