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Fifteen of every 100 couples in the world who want to have children find it difficult or impossible to conceive. In about half those couples, the male partner is infertile. Now researchers at the University of North Carolina at Chapel Hill Nutrition Research Institute in Kannapolis have found a possible genetic cause for some cases of male infertility.

A study led by Amy Johnson, Ph.D., a postdoctoral research associate working under institute director Steven H. Zeisel, M.D., Ph.D., has found that a genetic variant, called a single nucleotide polymorphism (SNP), is associated with human sperm motility. Between 5 percent and 10 percent of men are affected.

The SNP commonly occurs within the gene for human choline dehyrdogenase (CHDH) and can influence the amount of choline required in an individual’s diet. Choline, a nutrient used to form cell membranes, is found in eggs, meats and wheat germ, among other foods. 

The findings appeared in the April 27 issue of the journal PLoS One, published by the Public Library of Science (http://dx.plos.org/10.1371/journal.pone.0036047).

“The study is exciting,” Johnson said, “because we found that sperm from men who have this genetic difference look similar to sperm produced in mouse models that completely lack the choline enzyme.”

In both mice and humans, CHDH variant is associated with changes in sperm cell structural and motility, as well as lower energy levels.

“Often the cause of a man’s infertility is unknown,” Johnson said. “But we now have evidence that the CHDH SNP may play a role in some of these cases. This is encouraging because we know that dietary interventions can improve sperm energy levels and motility in mice.”   

Future laboratory studies will explore whether choline nutrient supplements also can improve sperm function in men with CHDH variations. 

Nutrition Research Institute contact: Beverly K. Jordan, (704) 250-5008, This e-mail address is being protected from spam bots, you need JavaScript enabled to view it