Study from Columbia University Medical Center shows that bones are connected with male fertility. Scientist in ahead of print report demonstrated that the skeleton, through a hormone released by bones, acts as a fertility regulator in male mice. This mysterious hormone is well known osteocalcin.

Researchers based their study on thesis that communication in our organism is rarely one-way. Therefore if the gonads regulate bones, there is a strong probability that bones regulate gonads. Laboratory mice answered the question. Previously it was observed that knock-out male mice (animals without osteocalcin secretion) were poor breeders. Scientist decided to explore this phenomenon.

Osteocalcin is also known as a bone gamma-carboxyglutamic acid-containing protein (BGLAP). It is secreted by osteoblasts located in bone and dentin. The main role of osteocalcin is bone-building metabolic regulation, so it’s often used as biomarker for the bone formation process. It is also affecting bone mineralization and calcium ion homeostasis. Other functions of this hormone is causing beta cells to release more insulin and fat cells to release adiponectin. Idea that osteocalcin may regulate the fertility is something new.

Columbia University Medical Center scientists discovered that osteocalcin is regulating the production of sex hormone – testosterone. Experiment in vitro showed increased release of testosterone after adding osteocalcin to the probe. After that observation, ostocalcin was injected into knock-out male mouse, which resulted with higher levels of circulating testosterone in those animals. It was obvious that osteocalcin-deficient male mice had lower concentrations of testosterone, which led to sperm count decline and decrease in number of pups per litter. This discovery wasn’t confirmed in humans yet, but there are observations that some infertile men have unexplained low levels of testosterone.

Unfortunately there are no reports in Columbia University Medical Center study that the skeleton or osteocalcin influence female fertility. It is well known that estrogen is controlling bone turnover and in women after menopause bone mass rapidly declines. Using the thesis, that communication in our organism is rarely one-way it is hard not to look for a connection between bones and ovaries. However, there are no new discoveries in that matter.

The next plan of researchers is to determine the signaling pathways used by osteocalcin to affect testosterone production. Moreover, the receptor of osteocalcin was indentified, so there is an opportunity to use a drug that mimics the function of this hormone. It would give a great benefit not only in managing the glucose metabolism, but also helping in reproduction, which is the essence of our lives.
This study was supported in part by the National Institute of Child Health Research (NICHR) and the National Institutes of Health (NIH).

Source:
1. Franck Oury, Grzegorz Sumara, Olga Sumara, Mathieu Ferron, Haixin Chang, Charles E. Smith, Louis Hermo, Susan Suarez, Bryan L. Roth, Patricia Ducy et al. Endocrine Regulation of Male Fertility by the Skeleton. Cell, 17 February 2011 DOI: 10.1016/j.cell.2011.02.004
2. Columbia University Medical Center (2011, February 18). Male fertility is in the bones: First evidence that skeleton plays a role in reproduction. ScienceDaily. Retrieved February 19, 2011, from http://www.sciencedaily.com­ /releases/2011/02/110217124909.htm

Author: Karolina Kłoda