According to published reports, male infertility is on the rise. In the last four decades, sperm counts worldwide have halved while sperm quality reduced disturbingly with 1 in 20 men identified with fertility. The critical reasons for male infertility include contacts with chemicals like plasticizers, bisphenol A, and phthalates, obesity, and late parenthood. However, according to Bedrich Mosinger, a specialist in the science of taste associated with Monell Chemical Senses Center, Philadelphia, the widespread use of fibrates in drugs and that of structurally-related phenoxy-herbicides in farming, blocks the human TAS1R3 receptor, and play a role in human infertility.

Interestingly, the fact that TAS1R is a taste receptor makes geneticist Mosinger’s claims unique. Since time immemorial, we have associated taste with food and survival. But if Mosinger is right, then, taste might have closer links with human procreation, than we ever thought possible. Mosinger, along with his team of researchers, studied the roles of the genes - TAS1R and GNAT3 – in mice and the course of their research uncovered something bizarre. The genes TAS1R3 and GNAT3 were found to be present in the testicles and sperm of mice. More precisely, the findings indicated connections of three single nucleotide polymorphisms (SNPs) in taste receptors genes (TASR) with male fertility.

His study findings, published in Proceedings of the National Academy of Sciences, says that the very genes that help us identify sweet and umami savours are also present in the testes and sperm of men and suppressing them might tamper not only with a man’s ability to taste but also his fertility. Explaining the taste mechanism Mosinger says as food comes in contact with the tongue, the taste receptors get activated and employ proteins to the nervous system to notify the brain about the flavours. He compares the taste receptor with a microphone and the proteins with its cable and says the taste of something is like hearing a sound by means of an amp, and on losing the mic or cable, the hearing process becomes incomplete. In the human body, the taste receptor (or mic) is controlled by the gene TAS1R, and the protein named gustducin (or cable) is the gene GNAT3.

With this surprising result, the scientists were further motivated to remove the genetic microphone and cable and study the consequences. The mice were genetically engineered to acquire the human versions of the TAS1R3 receptor while being devoid of the mouse version of TAS1R3 and GNAT3. On administering the drug clofibrate, which inhibits the human receptor, the male mice turned sterile, owning to deformed and lesser sperm. Also, the mice regained their fertility immediately after clofibrate was withdrawn from the diet. Another noteworthy finding was that no such effects were noticed in female reproduction, which Mosinger says helped them identify a fundamental role of the genes in male reproductive abilities.

Post-study, Mosinger and team enthused that if their pharmacological findings are associated with the global rise in male infertility rates, then the knowledge derived from the research will enable them to develop treatments to diminish or repeal fibrates and phenoxy-compounds’ effect on sperm quality and quantity as well as to prepare non-hormonal contraceptives for men. According to medical practitioners, the fibrates class of drugs and some herbicides, which are commonly used in treating lipid disorders, such as high blood cholesterol or triglycerides, have the potential to block expression of the gene TAS1R. Hence, usage of weedkillers like phenoxy herbicides along with a drug that inhibits the GNAT3 gene might affect one’s sperms. What needs to be done now is to understand the paths and methods in testes that make use of these taste genes. This knowledge will help scientists recognize how their loss causes male infertility.

Medically reviewed by Rishabh Verma, RP

Male genes linked to taste, play a role in fertility